Content uploaded by Michal Oleksowicz
Author content
All content in this area was uploaded by Michal Oleksowicz on Dec 25, 2018
Content may be subject to copyright.
European Journal of Science and Theology, June 2018, Vol.14, No.3, 77-94
_______________________________________________________________________
ARISTOTLE ON THE HEART AND BRAIN
Michał Oleksowicz
*
Nicolaus Copernicus University, Faculty of Theology, ul. Gagarina 37, 87-100 Torun, Poland
(Received 20 January 2018, revised 28 January 2018)
Abstract
„De Partibus Animalium‟ is a very significant part of Aristotle‟s work. There is strong
evidence that in this work of Aristotle we find a simultaneous development of the
zoological, biological and psychobiological issues which are significant for understanding
the position of Aristotle biologist and philosopher. On the basis of the „De Partibus
Animalium‟ it will be demonstrated how Aristotle understands the biological dimension of
the body. In the first part of this paper, the attention will be concentrated on role and
function of the heart. In the second part, the focus will be on the brain. In the conclusion
section, the main implications of the Aristotelian view of living beings and Aristotelian
methodology in Biology will be summed up. The aim of this work is to examine the basic
ideas of Aristotle as biologist and philosopher regarding the structure and functions of
heart and brain.
Keywords: history of science, philosophy of biology, Aristotle, anthropology
1. Introduction - Why ‘De Partibus Animalium’?
De Partibus Animalium (hereinafter PA) is a very significant part of
Aristotle‟s work for two reasons. Firstly, in the first section, consisting of book I,
is a general methodological introduction to the entire development of the
biological Aristotelian thought. It can be said that with the book of the PA the
biological thinking of Aristotle, at least in reference to his general theory of
Biology, starts in fact from zero 1. The second section of the PA (books II-IV)
consists of a theoretical investigation of huge empirical data, also collected in the
Historia Animalium (hereinafter HA). In fact the second section of the PA is
focused mainly on the anatomical and morphological point of view, enriched by
many references to physiological problems 1, p. 489-493; 2.
Secondly, the importance of the PA can be found in the fact that this work
was probably developed during the same period as the ontological studies
included in Aristotle‟s Metaphysica. Moreover, the De Anima (hereinafter DA)
was probably prior to it, and the De Generatione Animalium (hereinafter GA)
posterior 1, p. 486. Thus among the biological works of Corpus Aristotelicum
there are very significant and reciprocal interactions at the philosophical and
*
E-mail: oleksowicz.michal@gmail.com; additional contact information: Pontifical
Lateran University, Faculty of Philosophy, Piazza di S. Giovanni in Laterano 4, 00184
Rome, Italy
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
78
scientific level of explanation. All these factors can be considered as strong
evidence that in the PA, we find a contemporary development of the zoological,
biological and psychobiological issues which are significant for understanding the
position of Aristotle biologist and philosopher, and the foundation of his ideas
regarding the problem of human soul and the human corporality 1, p. 487-488; 3;
4.
2. The heart
Very important in the thinking of Aristotle is the question of the
relationship between the heart and the brain, which was for nearly two centuries
in the centre of philosophical and scientific debate in the ancient Greece. In this
debate two major currents of thought were presented 1, p. 543-549. The first
was accorded to Alcmaeon of Croton and his anatomical discoveries and the
second to Empedocles. Alcmaeon was probably the first one who practiced
dissection, which allowed him to discover the existence of channels (poroi),
connecting the sensory organs with the brain. It is not surprising to find some
concepts from Alcmaeon‟s epistemology in Aristotelian ideas, concerning the
problem of connecting the reality of experience, knowledge and techne. But,
contrary to Aristotle, Alcmaeon regarded the brain as the centre of perceptual and
intellectual human activity.
Empedocles emphasized the importance of the blood, and therefore
considered blood to be the seat of sensibility and thought. The reason for this
came from the theory that the blood is made up of the mixture of the four
elements (fluidity – the water, the heat – the fire, the density – the earth, the
mobility – the air). In this way, Empedocles believed that there is a close affinity
and immediate continuity between man and nature. Therefore, in Empedocles‟
approach there developed the idea of the progress of knowledge by analogy
(analogical method), since, according to him, nature manifested itself as a unitary
context, including in itself man and in any given experience the immanent
analogical relations 1, p. 548; 5.
The philosophical and scientific context of research in the mid of 4th
century BC provided Aristotle opportunity to consider the alternative of giving
greater importance to role and function of the brain or of the heart. If one chose
the brain, it became a choice of noetic structure of human knowledge,
predominantly understood as the heuristic, inductive method of apprehension with
a focus on the quantification of reality. On the other hand, choosing the heart did
not mean to focus on the interpretative and hermeneutic character of knowledge,
but rather to return to the manifesting force of reality, which reveals itself directly
through the phainomena, expressed in the reality of what actually is 1, p. 549.
2.1. The levels of the composition of living matter
At the beginning of the 2nd book of the PA Aristotle presents his theory of
the formation of living organisms that takes place on three levels of composition
Aristotle on the heart and brain
79
1, p. 540. Firstly, there is the composition resulting from the so-called elements
(stoicheia), namely earth, air, fire and water. But this idea is not only limited to
the doctrine of stoicheia, but also extends itself to the active qualities (dynámeis:
hot and cold, dry and moist).
In the PA Aristotle refers explicitly to the doctrine of the elements and the
qualities, which originated in the Empedocles‟ doctrine of four elements, and was
further developed in the writings of the syncretistic medicals from the late 5th and
the beginning of the 4th century, and is also found in the Platonic Academy.
Therefore, in the thought of Aristotle one finds influences from the Timaeus, but
also from the medical school represented by Philistion of Locri. The latter being
most probably the first to combine the doctrine of the elements with that of the
qualities. Aristotle uses these ideas in the discussion in the De Generatione et
Corruptione (II. 2-8), that consists in the statement that every natural body is
composed of all the elements and of all the qualities (II. 8). In fact, he assigns to
the four elements certain physical qualities, called the active properties
(dynámeis). According to Aristotle, there are four qualities (hot, cold, dry, moist),
and they must be coupled on the basis of the principle of opposites. But since the
contraries cannot form a pair due to the principle of non-contradiction, the
combinations of elements can only be four: hot-dry, hot-moist, cold-dry, cold-
moist 6.
Therefore, according to Aristotle, the elements and the qualities they make
lead to an emergence of a different mixis case by case, and the matter is going to
be qualified according to the prevailing dynamis in mixis. Aristotle considers the
states and the properties of matter as a transformation of dynámeis which is a step
forward. This renewed conception of dynámeis allows him to break the schematic
view of the elements-qualities, typical for the biological doctrines of ancient
physiologoi. Aristotle wanted to consider these qualities in relative rather than
absolute mode (PA 648b11). The theory of relativity of dynámeis leads to an
exploration these qualities in the tactile properties of the bodies, namely in their
capacity and the time needed for their heating, and in their capacity to be melted
and combusted 1, p. 540-542; 7; 8. In this way, according to the philosopher, the
body parts were constituted of the elements, which transferred to each of the
bodily parts the dynámeis. As a consequence, in the constitution of the different
parts the proportions of the elements could vary, that is, each part could assume
the predominant quality. These physical properties of a part were called
temperamentum or complexion 6, p. 29-34.
The second level of composition constituted of the elements and qualities is
the level of the uniform parts, such as bone, flesh and also to some extend the
blood. The properties of these parts depend strictly on the elements-qualities
prevailing in their composition. E.g. the blood is moist/hot, the bone is dry/cold.
According to the philosopher the aggregation of the elements formed the simple
and uniform parts, that, if decomposed or dissected, would provide smaller parts
all equal between them and equal to the whole. As Aristotle explains: “Of the
uniform parts present in animals, some are soft and moist, while others are hard
and solid. Those that are moist are either generally so or are so while in their
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
80
natural setting, e.g. blood, serum, soft fat, hard fat, marrow, semen, bile, milk (in
those that have it), flesh, and the parts analogous to these.” (PA 647b10-11) The
concept of uniform parts comes from Anaxagoras (De caelo, 302a) and was not
limited to animals, but referred to minerals and plants, which are also made up of
simple elements (Met., IV 388a) 6, p. 24-25.
The third and the last level of the composition is that of non-uniform parts,
such as face, hands, eye, nostril, entire arm and others (II. 1). In fact, different
uniform parts could be aggregated and thus form a complex part (not-uniform),
destined to different functions. Therefore the third level describes the parts that
perform a specific function, and they are called órgana (HA 488b27-30).
However, in general, the internal organs that perform a specific function (brain,
lungs, heart, kidneys, spleen, liver), are called splànchnon, viscera. These órgana
do not always correspond to organs in the modern sense. The hand, arm, face
considered by Aristotle as the órgana, are not properly organs. It should be also
mentioned that the heart is considered by Aristotle as belonging to both groups of
bodily parts. The brain is not included by the philosopher in any of the two
groups, because it “is neither a residue nor one of the continuous parts. Rather its
nature is distinctive; and it is reasonable for it to be this way” (PA 652b2-6). It
should be noted that the Aristotelian doctrine of uniform and non-uniform parts,
adopted by Galen, remained in use until the late 18th century, with the difference,
that the terms used by medieval and Renaissance authors to define the uniform
and non-uniform parts were respectively partes similares and dissimilares 6, p.
25-28.
However, there should be added the last, definitive level of the composition
– the body formed by the soul – that involves the aggregation of different organs
to form the unity of the living body. Aristotle thought that the Platonic
philosophers, and also his other predecessors, were not able to reach an
appropriate theory of the soul of all living beings (DA 403b20ff.). The innovation
of Aristotle consists in establishing the study of the soul as a general, biological
science, that it has a foundational role for other special biological sciences.
According to Aristotle the soul is not the body, but is what determines that the
body is alive. It is the primary and essential determination of a body capable of
living, equipped in organs suitable to perform the basic functions of life:
nourishment and development (DA 412a3ff.). His application of the doctrine of
the soul to the living makes clear that Aristotle admitted that most of the activities
of the soul have a psychosomatic nature. An exception is human thought (nous)
9. But the real element that connects souls with each other – the nutritive soul,
sensitive and rational – is rather a kind of basic, vegetative functions of all
livings. Aristotle also insists that the soul plays the causal role, namely the
formal-final cause and the moving cause of the living being 10.
2.2. The heart as a passage from the material aggregate to the body structure
As already mentioned, Aristotle distinguishes three levels of the
composition (sunthesis) of animals (PA 646a12). Therefore the elements supply
Aristotle on the heart and brain
81
the matter (hulē) for composite bodies (suntheton somaton), while the uniform
parts constitute the material basis for the non-uniform parts (PA 646a14ff.). Each
level has its own characteristics and fulfils its own role to provide the causes of
animal parts and their complex structures. Thereby Aristotle arrives at a question
that could be formulated in this way: “is the development of a living organism the
result of a sum of actualizations of element-potentials, or is it primarily the
actualization of a single potential for an organism of that form, a potential the
actualization of which involves the actualization of element-potentials, but is not
reducible to them?” 11. Up to this point the description of the genesis of the
body remains incomplete.
To give an explanation of the entire body as an organic composite in its
unity and totality (organon, PA 645b15ff.) Aristotle stresses that the elements are
a necessary pre-condition for the uniform parts, and the latter are necessary pre-
conditions for the non-uniform ones (PA 646b5-6). Thereby Aristotle states that
the non-uniform parts represent the telos, a limit (peras) in the process of
formation. Moreover Aristotle introduces a very important distinction between
instrumental (organikon) and sensory (aistheteron) functions in animals (PA
647a3ff.). This distinction suggests that the instrumental parts are not
homogeneous and that sensation takes place in the uniform parts (PA 647a4).
Thus, according to Aristotle, the problem of bodily unity consists in the issue of
the link between the sensory and the instrumental functions of body. This is so,
because entire animals (tois zôis holois, PA 646b17) perform polymorphic
(polymorphon) functions, and it is therefore necessary that the matter that
composes them possess different properties (dynámeis, PA 646b15-17). Hence
Aristotle‟s argument moves from the variability of functions and movements to
the varied powers of elemental parts, which is designed to perform different
functions. Now it is quite clear that the heterogeneity of functions is actually
related to the heterogeneity of the material elements (PA 646b18). This shows the
close link between inanimate and animate matter 12, 13.
However there remains the question how Aristotle wants to combine and
link uniform (sensory) and non-uniform (instrumental) parts 13, p. 91-94. It is in
this context that Aristotle arrives at a crucial explanation for the problem of the
heart. He notes that “since it is impossible to be an animal without perception, on
this account too it would seem necessary for animals to have some uniform parts;
for perception is in these, while actions are present through the mediation of the
non-uniform parts” (PA 647a20-23). In the next lines of text (PA 647a24-31) the
philosopher clearly shows an attempt to overcome the split between the
homogeneous and non-homogeneous parts, between sensory and instrumental
functions. The heart, or its analogous part, unites the body that would otherwise
be divided into two parts. The heart, on the one hand is divided into uniform
parts, but because of its shape (morphê) and configuration (schêmatos) it is non-
uniform. In other words, the heart as a material part is divisible into homogeneous
parts, but as a functional organ it is not divisible. Thus it can be said that Aristotle
describes here a kind of proto-structural part of an intermediate nature. In a
similar, proto-structural way he conceives of the veins (phleps) (PA 647b18-19).
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
82
According to him in one way the part of vein is homonymous with the whole
uniform part (vein), but on the other hand it is not homonymous, because literally
a part of a vein is not generally a vein (as the non-uniform). It means that proto-
structural is a type of an intermediate nature between uniform and non-uniform
parts somehow doubled as stuff and as structure. Now it is clear that the heart
plays a central role in the problem of passing from the material level of the
elements (mere aggregate) to the structural view of the animal body 7, p. 34-35;
12 p. 184; 14.
2.3. The heart as the principle of heat
The consideration of the heart as the natural principle is derived not only
from the issue of passing from the matter of the elements (mere aggregate) to the
structural view of the animal body, but also results from the physiological
privilege of the heat itself. How does Aristotle demonstrate the role of the heart as
a natural principle and as a seat of the heat? In the case of the heart as the source
of blood, his proof included in the text PA 647a30-1 could be reconstructed as
follows:
Premise1) The heart is the origin of blood and is not present in bloodless animals.
Premise2) Perception, movement, nutrition are present in all animals – blooded
and bloodless.
Conclusion) So bloodless animals they must have an analogue of the heart 12, p.
184.
In the case of the heart as the seat of the heat J.G. Lennox proposes to reconstruct
Aristotle‟s demonstration on the base of premises that come from the
Meteorologica IV. 1-2, in the following way:
Premise1) All growing things must take in nutrients.
Premise2) All nutrients are derived from moist or dry material.
Conclusion1/Premise3) All growing things must take in moist or dry material.
Premise4) Moist or dry material is transformed or digested (pepsis) into nutrients
by heat.
Conclusion2) So all growing things must have a source of heat 12, p. 198-199.
More precisely, what is the role of the innate heat? The idea that the animal
heat could play an important role in biological functions had already been
developed by Parmenides, Empedocles and other Hippocratic authors. For
Aristotle, the heat was sýmphyton, that is, the innate or connate with the animal‟s
life, and ensured the growth and nourishment of all living beings. It must be said
that ancient theorists never raised the question as to how and according to what
the innate heat had been originated. Therefore these explanations were far away
from the idea that the heat comes from chemical reactions or cellular metabolism.
Generally, in blooded animals, heat was thought to be responsible for digestion
(pepsis), which is a series of chemical reactions that transformed food into blood.
The last one was understood as a final nourishment for all parts of the body (PA
650a34). In this way the heart, as the natural seat of the heat, had the function of
forming the blood (HA 520b10). The philosopher divides digestion in three
Aristotle on the heart and brain
83
phases: the first, the mechanical process of chewing, then the second phase in the
stomach, and the third in the ventricle of the heart (production of pure and sincere
blood, PA 650a3-b10; De Juventute et Senectute, 469a1-5). Then Aristotle goes a
step further, arguing that the principle of life, the heart with its innate heat, cannot
have a different location from that of the principle that analyses sensations and
produces movements (De Juventute et Senectute, 469a16-27). Therefore, for the
philosopher an animal is characterized by vital processes and the ability to feel.
The notion that the heart was the hottest viscera of the whole body, survived
unchanged for nearly two millennia, until the experiment of Giovanni Alfonso
Borelli in 1680, who by the use of the thermometer demonstrated that the
temperature of the heart was not higher than other viscera of human body 6, p.
106-111.
2.4. The heart as a principle of perception and movement
In the PA we lack the systematic description of the nervous system
conceived in contemporary terms, as opposed to descriptions of other systems.
However, the heart plays the role of being the centre of perceptual activity
(656a26-8; 666a34-5). In fact, as Aristotle observed, channels (póroi) are spread
from the eyes and ears, which arrive at the veins around the brain, and from there
the stimulus comes back to the principle, that is to the heart (656b16-20; cfr. GA
743b35-744a6). In his discussion on perception it can be seen that for Aristotle, at
the functional level, the topographic contiguity of the channels had no decisive
significance in the theoretical explanation of perception. Instead, he used the
principle of the association of similar 4, p. 621; 15. To understand this point it
has to be mentioned that Aristotle, as some of his predecessors, associated the
senses to the elements: water to sight, hearing and smell, respectively to air and to
fire; taste and touch, considered as analogous, to earth. The logic of this
association is explained in the different works (De Sensu et Sensibilibus, 438b18-
439a1-5; cf. DA 425a5-15). In this way, the doctrine of senses associated with the
elements was applied to the topography of the spatial relations between the sense
organs and the brain or the heart 6, p. 73-75.
Aristotle demonstrated through dissections that the main sensors are
connected to the heart thanks to the blood vessels (phlébia). Because his ancient
predecessors did not know about nerves, the channels were called póroi or
phlébia. Plato, Hippocratic physicians, Alcmaeon, Anaxagoras had indicated the
brain as the seat of the arrival of all sensations. However it had not escaped
Aristotle that Plato in Timaeus indicated that some feelings could come to the
liver and to the heart (65d-66a, 67b). The teachings of Empedocles held that the
blood is the instrument of perception and knowledge, and explanations of
Diogenes of Apollonia also argued that sensations could spread throughout all the
body by the phlébes 5, p. 627-629. All these ideas formed the theoretical basis
for Aristotle‟s thesis of the link between the sense organs and the heart. However,
apart from the arguments of his predecessors, Aristotle was also performing many
anatomical dissections, looking for the channels between the senses and the heart.
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
84
Thereby he states that the channels of the eyes communicate with the veins
around the brain (PA 656b17; cfr. HA 495a11-17). In addition, the philosopher
says explicitly that the touch and the taste “are evidently connected to the heart”
(PA 656a30-31; cfr. De Sensu, 439a1-2), but does not explain more precisely why
is so 6, p. 80-82.
According to the philosopher, the perceptive-sensory apparatus consists of
two different groups of senses and their respective organs. The first group
contains the senses of touch and taste, and its organ is the flesh, because it
receives the sensation from the outside and transmits it to the heart. The flesh is in
fact the primary sense-receptor (PA 653b24). The animal is, by definition, that
what possesses the senses, and in the first place the first of the senses, the touch.
In fact Aristotle observes that “and since perception is present in the simple parts,
it is perfectly reasonable for touch to arise in a uniform part, and yet in the least
simple of the sense-receptors; for it most of all seems to be a perception of many
kinds of things, and the sense-object related to it seems to have many
oppositions” (PA 647a12-17). Thereby it is necessary that sensations take place in
the uniform parts. Moreover the flesh (the sense of touch) and the tongue (the
sense of taste), are the instruments of tactile faculties (DA 423b26), while the
primary sensory, that is the place where occurs the perception, is not the flesh (PA
656b35-36), but the inner part of the body – the heart (De Sensu 439a2; PA
656a29). The second group consists of the senses of smell, hearing and sight (II.
10). The organs of these senses are in the head, because they need pure and cold
blood. And also in this case, in a similar way, the channels convey the sensation
to the veins and from them the perception reaches the heart 6, p. 82-83; 14, p.
550. The channels of all sensors are stretched to the heart, and in the animals
lacking the heart to its analogue (GA 781a21). Therefore the heart becomes the
seat of the sensitive soul, so plays a role of the common sensorium (koinòn
asthetérion). What Alcmaeon had attributed to the brain, Aristotle attributed to
the heart.
It should be noted that for the philosopher the heart was not only the place
where all the sensory data from the senses converges, but also the origin of all
movement (PA 665a10-15). As already mentioned, Aristotle was far from
knowing that nerves act in order to contract muscles. Nerves will be explicitly
identified and distinguished in terms of sensory (aisthetikà neûra) and motor
nerves (proairetikà neûra) a few decades later than Aristotle by two medical
theorists: Herophilos of Chalcedon and Erasistratus of Ceos. Aristotle did not
distinguish between tendons, ligaments, muscles and nerves. Consequently, the
term sinew (neuron), used by him and by all physicians and philosophers who had
preceded him, denotes the anatomical element that links bones together or
muscles and bones together, that is the tendons and ligaments. In fact, in the PA
Aristotle explains that the heart has plenty of neûra and that these elements can
generate motion by contracting and relaxing (PA 666b14-17). According to the
philosopher the heart possesses in its cavity the sinews, and from the heart
diverge sinews as the aorta is a similar vein to a sinew. Therefore it is clear that
for Aristotle the active part of the muscle contraction was not played by muscle,
Aristotle on the heart and brain
85
but by sinews, that is tendons and fibres derived from blood vessels. These last
proceeding to “the periphery” of body become smaller and are transformed into
solid elements. By their aggregation they become sinews (PA 666b14ff.). Now it
is clear that it makes no sense to attribute to Aristotle the enormous absurdity of
deriving all the nerves from the heart 6, p. 86-91.
The last step taken by Aristotle to explain voluntary movements consists in
the doctrine of pneûma, which was not invented by Aristotle, but came from a
long ancient tradition. On the one hand, this theory had its origin in the
conception of the Homeric thymós (the inhaled air gave man life and intelligence),
and on the other hand in the doctrine of the psyché of Diogenes of Apollonia (the
soul as a special entity: psyché-aria-noûs). In the complex doctrine of pneûma that
came from Galen, the pneûma was considered as the air elaborated at the heart
level and transformed, thanks to the vital heat, into pneûma zotikón (vital spirit).
That was then transmitted through the arteries to all parts of the body, giving them
the ability to perform their functions. However, there was a quantity of pneûma
zotikón destined to go to the brain, and this quantity underwent further elaboration
to become pneûma psychikón (animal spirit), that is, the spirit by which all
operations of the mind are possible. To be precise, Aristotle did not formulate an
organic doctrine of pneûma, but he referred to it in his different works in order to
explain many physiological functions. However there is a substantial difference
between the Aristotelian doctrine of pneûma and those professed by other
physicians and philosophers. For the philosopher, the pneûma was aerial, hot
substance, of not external but internal origin. Therefore it was the kind of innate
or connate substance, called the sýmphyton pneûma. It originated inside the body
by the effect of the internal heat and it could be turned into steam, or it could be
derived from evaporation of the blood. In fact, if the blood evaporation occurred
in the heart thanks to the innate heat, the heart is also the seat and origin of breath
(pneûma, PA 667a28). Although Aristotle, suggested a close relation between the
pneûma and soul, he did not identify them, but made from the pneûma the
instrument (proton órganon) of the psyché (GA 762a19-23). Now it seems clear
that the philosopher could assign to the pneûma the role of the agent of
sensations, because sensations had been conceived as a movement, where the
stimulus moves the sensory and this movement must be transmitted to the
common sensorium (DA 416b33, 417a15-21; De Sensu 447a15-29). In other
words, the stimulus acts by moving the respective sensors, and the latter must
transmit the movement (kínesis) to the heart, where perception occurs 6, p. 92-
97. It is important to add that the heart is also the seat of the most complex
sensations, human emotions (PA 666a11-12). This observation is related to
Aristotle‟s criticism of the argument from the Timaeus (70C), that the lung serves
to calm down too violent palpitations (pēdēsis) of the heart. According to the
philosopher “it has been claimed – incorrectly – that the lung is connected with
the leaping of the heart; I say „incorrectly‟ because the occurrence of this leaping
happens only, roughly speaking, in mankind, because mankind alone becomes
expectant and hopeful for the future. Moreover, in most animals the heart lies at a
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
86
great distance from, and in a location higher up than, the lung” (PA 669a18-22).
Here Aristotle does not mean that beat of the heart (halsis; that is the pulsation of
the heart; cfr. De Respiratione, 479b18ff.) only occurs in the case of humans, but
he refers here to the exceptional pulsations caused by emotions 4, p. 657; 1, p.
550. In the PA the phainomena revealed by sensitive observation (aisthēsis) are
considered as an immediate manifestation of reality. Therefore the task of logos is
to organize and reconstruct them. In the Parva or De Anima this kind of
continuity of the perceptual-cognitive process begins to change, because what is
perceived is no longer considered as the simple object (real ousia), but as a set of
the sensory qualities 4, p. 34-35. Thereby in the Parva the cardiocentric thesis
becomes more nuanced, because it is framed in the psycho-physiological
investigation linked with the aforementioned doctrine of pneûma, resulting in the
idea that the function of the sensory faculty consists in cognitive functions that is
the perception 10, p. 153-159.
3. The brain
At the time of Aristotle, there were two opposing concepts of the role of the
brain. The first one, outlined by Anaximenes, considered the brain as the seat of
intelligence. The first main representative of this conception Alcmaeon, has been
already mentioned, who was followed by the Pythagoreans, Democritus,
Diogenes of Apollonia, the author of On the Sacred Disease and Plato. The other
conception could be attributed to Heraclitus and his followers, who saw in the
innate heat the principle of life and the divine element in man. As mentioned,
Empedocles is one of the greatest exponents of this view. This position was later
on developed by Aristotle 16. From what has been said so far results that
Aristotle believed that the fundamental factor of all life processes was made up of
the innate heat placed in the heart (the hearth of the body). Thus the role of the
brain, that is, as the centre of perception and thought, was assigned by Aristotle to
the heart 17. Since Aristotle believed that there was no direct connection
between the brain and mental faculties, his research was directed to the moist and
fluid nature of the brain (PA II.7 652a27-29), and the brain was downgraded to a
mere refrigerant organ of the cardiac heat. This approach, that classified the brain
as a cold organ, actually persisted in the history of science until the 17th century
16, p. 604-605.
3.1. The process of cooling
It seems that the main reason that led Aristotle to provide the theoretical
explanation of the brain comes from his concept of finality present in natural
processes (PA 645a24-26). According to the philosopher, scientific explanation
must investigate the teleology, because “that for the sake of which and the good
are present more in the works of nature than in those of art” (PA 639b19-21).
Aristotle, assured by the principle that nature does nothing in vain, and that the
Aristotle on the heart and brain
87
phainómenon is always true and guaranteed, tries to give an account for the
theoretical foundation of the phainómenon in his investigations. Sometimes this
means that the facts that could not be explained by the scientific knowledge of his
time, or the facts coming from only partial observations, were sufficient for him
to put in motion the whole „machine‟ of his science, to create theoretical
explanations of the facts not correctly established 1, p. 531. A clear example of
this can be found in the explanation of the fact that man is the only living being
having buttocks (PA 689b15-22). It is likely that on the base of his desire to
explain differences in animals in a teleological way, sometimes at all costs,
Aristotle developed the theory of why nature provided a brain to humans and all
blooded animals. The philosopher did not have any intuition of any precise
function of the brain, except for its features like coolness and humidity.
Consequently, he used these notions, derived from the evidence of his
experiences, to assert that nature has furnished all blooded animals with cold and
moist brains, with the unique purpose to temper the innate heat 12, p. 315-316.
In fact, in the PA Aristotle describes the principle of balance between
opposites, the principle also called the principle of compensation (652a30-33). He
applies this principle to the brain and to the heart, explaining that the brain
belongs to animals for the preservation of their entire nature (652b6-7). This
preservation consists in tempering by the brain the heat and the boiling that take
place in the heart (652b6-26). This passage contains the essence of the
Aristotelian theory of the brain‟s function, namely the role of cooling the region
of the heart. In other words, the brain and the heart are mutually connected in a
close manner. The heart could not perform its functions without the cooperation
with the brain 16, p. 605; 6, p. 101-105. It should also be pointed out the
reasoning that the philosopher uses to exclude the possibility that the brain could
have had any other function than cooling the heart (PA 652b23-6). His
demonstration could be reconstructed as follows:
Premise1) All animals by nature have at least one organ of perception.
Premise2) If the brain subserved cognition, all animals would have one.
Conclusion) Because the bloodless animals do not, its presence must be explained
otherwise.
It should be noted that even if the philosopher attributed to blooded animals
a part analogous to the heart, he did not perform an analogical explanation in
respect of the encephalon. The unique exception to this, mentioned by Aristotle,
was the octopus, considered to have a part analogous to the brain. Also in the HA
(494b28, 524b4) the cephalopods are deemed to have an analogous part to the
brain 12, p. 209-210.
What is the more specific sense of the Aristotle‟s theory of cooling the
body? The heart, in the Aristotelian conception, should be well protected and
safeguarded from the excess of the heat via the mechanism of thermoregulation.
In other words, the main preoccupation of all ancient medicine and natural
philosophy, did not concern the problem of production of the heat (energy
metabolism or heat preservation), but rather the issue of efficient heat dissipation
in the body. Thus, it was necessary to find the mechanism of the cooling of the
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
88
heart. Generally the explanation of Philistion of Locri, Diocles, Hippo, Philolaus
dominated, namely, that this function was assigned to the breathing process
performed by the lungs and even the skin pores. Also Plato assigned to the air,
and in part also to the fluids entering through the trachea, the function of
moderating both the heat from the heart and the heat coming from passions
(Timaeus, 70a-d) 6, p. 112-114. However, Aristotle offers a somewhat different
description of the cooling process. According to him, that process is similar to the
formation of rain. The hot steam ascends in the upper parts of the atmosphere and
is condensed because of the cooling and then it comes down as rain, bringing
refreshment to the earth (PA 653a5-10). He proposed the same mechanism to
explain sleep (De somno et vigilia, 456b17-24, 457b30-458a6). However, the
philosopher did not provide any additional explanations on the matter of this
process. The Aristotelian theory of the brain function was strongly criticized by
Galen, who claimed as Plato (Timaeus, 70d), that the process of breathing is
enough to cool the heart 6, p. 118-119; 12, p. 210.
It should be mentioned that the Aristotelian explanation of the cooling
system mentions not only the brain (II. 7), but also the role of lungs and gills (III.
6). According to Aristotle “it is necessary for cooling from without to be either by
water or by air” (PA 669a1). In the lungs, cooling is accomplished through the
inhaled air. In the bloodless animals this function is accomplished by the innate
pneûma, but in fish through the presence of gills. The lungs are closely related to
the heart, because they receive from it the principle of movement. Moreover
according to the philosopher, the lungs are blood free, in the sense that they do
not have the blood in themselves. However Aristotle notes that the lungs are
porous and rich of numerous veins that contain the blood 1, p. 545-546, 551.
As mentioned above, for the ancient physicians and philosophers the
problem of regulation of the heat was the main issue of the functioning of the
living beings, namely of their vital homeostasis 13, p. 91. According to them,
the preservation of life and the proper functioning of the whole organism strictly
depended on the process of heat dissipation. In the fragments of the De Juventute
et Senectute (469b21-25; 474b20-24) the philosopher explains the two ways in
which the heat is destroyed: the consumption and the extinction. The first consists
in the destruction produced by itself while the latter in the destruction produced
by contraries elements. Aristotle adds that the first process is caused by the heat
excess. In other words, consumption is described as the destruction of the heat by
the heat excess and this destruction is called the death. In the De Respiratione the
philosopher explains that the nature of animals needs the cooling, because of the
inflammation of the soul in the heart. This cooling in animals is accomplished
through the respiration. Those who have the heart, but not the lungs, such as
fishes, cooling is obtained thanks to the water through the gills (478a30-34).
Moreover, in these passages, Aristotle mistakenly understood hyperthermia as
death by suffocation. Thereby the fresh air entering by inhalation, not only acts as
instrument of cooling that regulates heat, but also as instrument of inflammation
and therefore sustains the innate heat. In this explanation the air was providing
simultaneously two opposite processes: cooling and heating. Aristotle also
Aristotle on the heart and brain
89
assigned to the lungs and to the breathing process, the function of supplying the
air to the heart (HA 495b8-12). This air, according to some theories (also in the
interpretation of Galen), is then used together with the steam coming from the
blood and with the air coming through the skin pores, for the formation of the
vital pneûma. Thus after Aristotle for centuries the main functions of the
pulmonary ventilation will remain two: the moderation of the animal heat and the
air supply for the formation of the vital pneûma 6, p. 114-116.
Aristotle was also aware of the link between the brain and the spinal
marrow, but this relation is explained very briefly in relation to the scheme of the
cooling process. That is, through the spinal cord, heat is transported to the brain to
be cooled. Plato argued in Timaeus (75c-d), that the brain has a nature of the
marrow. However, Aristotle had no doubt about the opposition of its nature: the
marrow is naturally hot, while the brain is among the coldest of the parts within
the body (PA 652a24-33) 13, p. 89-90.
It could be said, that on the theoretical premises of the Aristotelian
description of the cooling mechanism, the latter could be also used to heat the
brain, namely that the heart would heat the brain through the blood. However, as
already mentioned, Aristotle proposed that the brain cooled the heart. The brain
system, in Aristotle‟s theory, appears as a radiator to dissipate the innate heat,
keeping stable the heat in the heart. His position could probably be explained in
light of the fact that Aristotle did not know about the circulation of blood. Like
Plato (Timaeus, 77c-d, 79a), he believed that the blood vessels spread out from
the heart to the whole body as gardens aqueducts are constructed from one origin
and spring into many channels (PA 668a14-35). In this way, the flesh consumes
the blood produced in the heart thanks to the action of heat under the raw material
coming from the digestion 6, p. 117-118.
To sum up, it should be stressed that the theory of the refrigerating did not
have a great follow-up in future research. Among the reasons for its lack of
impact could due to one of the most important discoveries in the history of
neuroscience, made only a few decades after the death of Aristotle, by Herophilos
of Chalcedon and Erasistratus of Ceos: namely, the identification of the sensory
and motor nerves as having their origin in the brain. Consequently, the results of
their research were adopted in the medical field by Diocles and Praxagoras of Cos
and then accepted by the medical sect of Pneumaticos. Galen also followed this
research, demonstrating that the rational faculty is localized in the brain. Although
he did not preclude that emotions could have their origin in the heart. Thanks to
these theoretical approaches, the brain became to be considered as the center of
perception and sensory integration 6, p. 141-147.
3.2. The brain and perception
The anatomical investigations of Aristotle convinced him that all the
processes of perception did not take place in the brain, but, as already explained,
in the main organ (arché) – the heart. There are three main empirical proofs upon
which he based his reasoning in reaching this conclusion.
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
90
The first one was derived from the results of a very simple empirical test.
Aristotle believed that nothing bloodless is capable of perception, nor is the same
blood capable of perception (PA 656b19-20). On the base of this reasoning, the
philosopher argues that even the brain does not have any perceptive faculties (PA
652a35-b1; 656a23-25). His conclusions about the insensibility of the brain
substance comes from the proof of mechanical stimulation of the brain (PA
652b3-6; HA 520b16), in that the brain does not register sensation when is
touched. These texts imply that Aristotle performed the vivisection, although it is
not specified what kind of animals he used. Aristotle expected that if the animal
had felt the stimulus applied to his brain, the animal would have reacted,
recording a sensation. However, when he mechanically stimulated the animal
brain, he did not observe any animal reaction. It must be said, that the result of his
experiment was correct. In fact, the brain and the pia mater have neither touch-
pressure receptors nor nociceptors. However, it was incorrect to draw the
conclusion from this experiment that the brain could not have any relations with
the problem of perception 6, p. 71-73.
The second proof is based on the aforementioned principle of the
association of similar, and serves to justify the presence of the main sense organs
in the head, but without investigating its functional link with the brain. That
principle was based on the evidence of material similarity between properties of
senses and material elements constituting them. The channels of communication
originated in the eye sensors, called póroi, in the HA (492a21) are distinguished
into three types, spreading from the eye to the brain. One couple of these three
channels could be identified as the optic nerves that cross together in the form of
chiasma. However, these channels (póroi), according to Aristotle, do not serve to
transfer the visual information, as happens in the case of the Alcmaeon theory. In
the GA (744a7-8), examining the eye and the brain development, Aristotle focuses
on the fact that the eye is moist and cold, and that from the brain coolness the
purest part of the coolness is transported by the channels and is lead through them
to the membrane around the brain. In this way he explained the watery quality of
the organ of sight 15, p. 221. Thus, Aristotle interpreted the eye‟s affinity to the
brain not because of the discovery of the optic nerves, but in virtue of the idea of
the association of similar properties.
The presence of the sense of hearing in the head is justified by a similar
logic. According to the philosopher, this sense is located in the head for two
reasons: firstly, that the channel that departs from the ear ends in the back part of
the head; secondly, it must be located in proximity to the air in that part of the
skull (PA 656b13-19). It seems that Aristotle was first to articulate the precise
description of the complicated network of canals in the petrous temporal bone and
identified the cochlea (HA 492a19; DA 420a13). To understand better the
aforementioned second proof, it must be said that the ancient philosophers and
physicians believed that the cavity defined cochlea contained the innate and
immobile air, which remains closed inside the ear. Thereby they believed that the
main organ of hearing was this air. Aristotle also believed that the back part of the
skull was full of air (HA 491a30, 494b33-34; GA 784a1-3, 784b35, 785a1; PA
Aristotle on the heart and brain
91
656b12-13). Now it is clear that if the air was connected with hearing and was the
conductive element of sounds, it had to be placed in proximity to the air contained
in the back part of the skull (PA 656b14-19). The eye had been placed in the head
because of the presence of the watery viscera, so hearing had to be placed in the
same place, but because of the proximity with the air in the back part of the skull
12, p. 225.
Even for the sense of smell the same reasoning is used, based on the
principle of similar, but the explanation remains less clear. According to the
philosopher, by nature the aroma is naturally warm and thus is associated with the
brain (De Sensu, 444a25). The brain as a cold organ could have easily cooled the
blood contained by the body, so the smells available to man, prevent that process
with their heat, for the protection of human health (De Sensu, 444a9-25). In this
case, the idea of the association remains the same. However, the strength of the
argument seems to be weak and confused 6, p. 73-80.
To sum up, according to Aristotle, the brain does not have anatomical and
functional relations with the sensory organs. At this point it is worth emphasizing
two things. The first, that already in ancient times there had been established a
kind of general rule to counteract the insensitivity of the brain to the strong
sensitivity of the meninges, e.g. Erasistratus of Ceos had classified the brain
between the parenchýmata (the parts of body lacking sensation), while the dura
mater was classified as triplokía (the structure provided in sensitivity).
Consequently, some historians attested that Erasistratus had placed the seat of
hegemonikón in the dura mater, however Galen argued that Erasistratus identified
the origin of the nerves in the brain. The Aristotelian observations of brain
insensibility were widely confirmed also by Galen. The latter claimed that the seat
of the hegemonikón is in the brain, because that is where we find the origin of the
nerves, and therefore has to be the location of the main part (hegemonikón) of the
soul 6, p. 89. In his proofs he demonstrated that all the nerves are originated in
the encephalon and he reflected on the contradiction between the role of the brain
in sensory perception and its insensitivity to the application of mechanical
stimulus. He explained that the brain is not a sensory organ, but rather the organ
that interprets sensations, and called it “the sensorium of the sensors”. The second
thing worth noting is that about twenty three centuries after Aristotle, the
exploration of the cerebral hemispheres of man provided by H. Cushing (1909)
and W. Penfield (between 1928 and 1947) showed that the brain actually does
„feels‟, if it is stimulated adequately; but it cannot „feel‟ itself because does not
have receptors 6, p. 179-194.
4. Conclusions
The study of Aristotle‟s discussion of the heart reveals the application of
his theoretical concepts of the animal systematic and the composition of living
beings. Because the heart is considered by him to be the principle of life, of
perception, the motor processes, the animal heat, the nourishment and the growth,
it can be said that in some way his conception of organic life circulates around the
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
92
theory of this organ. The study of all natural processes linked with the heart
shows the theoretical background of his vision of living nature, and helps to see
his philosophical concepts grounded in his biological research. In the PA the
philosopher assigns to the heart the role of the centre of perception and psychical
capacities, developing the thought of Empedocles, Philistion of Locri and
Philolaus. He attributes to the vascular system the role that would later be
assigned to the nervous system. On the one hand Aristotle goes a step further,
providing a somatic foundation of the psychic functions and connecting them
strongly with organic actions, but on the other hand he is backtracking, because
he did not recognize the functional connection between the sense organs and the
brain 4, p. 32-33.
From the modern point of view Aristotelian explanations of the brain seem
to be absolutely worthless. However, framed in his investigation of the body, they
represent a set of important explanations 18. First of all, the study of the
problem of the brain reveals much information about the scientific investigation
of the time, about the way of doing observation provided by the ancient
physicians. Furthermore, the cooling theory showed a strong thermodynamic
approach presented in his study of the living beings. Thus, considering the brain
as the cooling organ of the body, of the heart, does not mean only the
subordination of the former to the latter, but also shows a complementary, holistic
vision of natural processes acting in the organism. In other words, the
abovementioned principle of the compensation (or organic equivalents or organic
balance) expresses this Aristotelian vision of living nature.
From the discussion about the role of the brain we may derive conclusions
about the problem of perception. It is probable that in the historical context of the
research conducted by Aristotle, the theory of nerves in the human body had not
yet been established and therefore he had to search for other theoretical
approaches to explain the connection between the sense organs and the important
organs for the functioning of the body. Thus, Aristotle chose the principle of the
association of similar (that is the similarity between the organs and the material
elements) to interpret the closeness of the senses to the brain. A naïve theory,
from the contemporary point of view, however, in that context, is providing
physical and physiological explanations of life processes.
Aristotle was that researcher who developed a very complex system of
thinking, in many ways near to the modern scientific view. Thanks to his
conception of physics based on the four causes and the four elements included in
organisms; the conception of the living having in itself the principle of motion;
the description of different properties increasing in complexity starting from the
plants, via the animals to the man, Aristotle‟s biology had acquired, for the first
time in human history, a systematic approach to the issue of living nature 19.
Thus a great merit of Aristotle as philosopher and biologist is to have founded the
science of Biology and the philosophy of Biology. Consequently the Aristotelian
inheritance has dominated human thought until the nineteenth century, with a
success comparable only to the Euclidean geometry systematization 10, p. 173-
174. The strength and the depth of the Aristotelian study of nature was grounded
Aristotle on the heart and brain
93
in his philosophical ability to wonder in front of reality, since “in all natural
things there is something marvellous” (PA 645a16-17). The genius of Aristotle
the biologist would not exist without Aristotle the philosopher.
Acknowledgment
Many thanks to Jennifer Bullington who read the manuscript and suggested
valuable improvements.
References
[1] M. Vegetti, I fondamenti teorici della biologia aristotelica nel De partibus
animalium, in Opere biologiche di Aristotele, D. Lanza & M. Vegetti (eds.), UTET,
Torino, 1971, 492-493.
[2] J.G. Lennox, Aristotle’s philosophy of biology. Studies in the origins of life science,
CUP, Cambridge, 2001, 7-109.
[3] D.M. Balme, The place of biology in Aristotle’s philosophy, in Philosophical issues
in Aristotle’s biology, A. Gotthelf & J.G. Lennox (eds.), CUP, Cambridge, 1987, 16.
[4] D. Lanza and M. Vegetti (eds.), Opere biologiche di Aristotele, UTET, Torino, 1971,
13-14.
[5] H. Diels and W. Kranz, Die Fragmente der Vorsokratiker. Berlin, 1960-1961, in I
presocratici. Testimonianze e frammenti, G. Giannantoni, R. Laurenti, A.
Maddalena, P. Albertelli, V.E. Alfieri & M.T. Cardini (eds.), Laterza, Roma-Bari,
1969, 361-367, 402-403.
[6] T. Manzoni, Aristotele e il cervello, Carocci, Roma, 2007, 29.
[7] M. Furth, Aristotle’s biological universe: an overview, in Philosophical issues in
Aristotle’s biology, A. Gotthelf & J.G. Lennox (eds.), CUP, Cambridge, 1987, 21-52.
[8] L. Rossetti, Aristotele, in Dizionario delle scienze e delle tecniche di Grecia e Roma,
P. Radici Colace (ed.), Vol. I, Fabrizio-Serra, Pisa-Roma, 2010, 187-188.
[9] W. Charlton, Aristotle on the place of mind in nature, in Philosophical issues in
Aristotle’s biology, A. Gotthelf & J.G. Lennox (eds.), CUP, Cambridge, 1987, 408-
423.
[10] E. Berti, Guida ad Aristotele, Laterza, Roma-Bari, 2004, 143-153, 189-190.
[11] A. Gotthelf, Aristotle’s conception of final causality, in Philosophical issues in
Aristotle’s biology, A. Gotthelf & J.G. Lennox (eds.), CUP, Cambridge, 1987, 212.
[12] J.G. Lennox (ed.), On the parts of animals, Clarendon Press, Oxford, 2001, 183.
[13] J.A. Tipton, Philosophical Biology in Aristotle’s Parts of Animals, in Studies in
history and philosophy of science, Springer, Heidelberg, 2014, 75-78.
[14] M. Vegetti, Origini e metodi della zoologia aristotelica nella Historia Animalium, in
Opere biologiche di Aristotele, D. Lanza & M. Vegetti (eds.), UTET, Torino, 1971,
79-81.
[15] G.E.R. Lloyd, The Empirical Basis of the Physiology of the Parva Naturalia, Proc.
of the VIIth Aristotelicum Symposium: Aristotle on Mind and the Senses, G.E.R.
Lloyd & G.E.L. Owen (eds.), CUP, Cambridge, 1975, 215-239.
[16] I. Düring, Aristotele, Italian translation, Mursia, Milano, 1966, 604.
[17] M. Vegetti, Aristotele, in Dizionario delle scienze e delle tecniche di Grecia e Roma,
P. Radici Colace (ed.), Vol. I, Fabrizio-Serra, Pisa-Roma, 2010, 191-192.
[18] G.E.R. Lloyd, Empirical research in Aristotle’s biology, in Philosophical issues in
Aristotle’s biology, A. Gotthelf & J.G. Lennox (eds.), CUP, Cambridge, 1987, 55-56.
Oleksowicz/European Journal of Science and Theology 14 (2018), 3, 77-94
94
[19] F. Cuzari, Vita, in Dizionario delle scienze e delle tecniche di Grecia e Roma, P.
Radici Colace (ed.), vol. II, Fabrizio-Serra, Pisa-Roma, 2010, 1012-1013.
