Peter Øhrstrøm

• Professor, D.Sc., Ph.D.
• Professor (Full) at Aalborg University

A.N. Prior (1914-69) presented his tense-logic for the very first time at the New Zealand section of the Australasian Association of Psychology and Philosophy, Second Philosophical Congress, Wellington 27th – 30th August, 1954. He introduced his ideas as a new and important approach to the discussion of basic aspects of time. It is, in fact, remark...

Current genetics studies often refer to notions from information science. The purpose of this paper is to summarize and structure the different notions of information used in biology, as a step towards developing a taxonomy of information. Within this framework we propose an extension of Floridi’s conceptual model of information. We also make use o...

In his paper “Opposite Number” (1957) A.N. Prior anticipates the later philosophical debate on the ideas of bifurcation in time, existence and identity. The paper was inspired by a science fiction story by John Wyndham, and it was published in 1957, i.e., the year before Kripke´s famous letter of September 3, 1958, in which the idea of branching ti...

This paper describes the analysis of streamed log data generated from the use of two specific e-learning tools in the context of a basic logic course taught and evaluated at Aalborg University, Denmark, during the period from September 2022 to January 2023. The students’ work with the two kinds of basic logic introduced in the course, classical syl...

In his famous letter to A. N. Prior dated 3 September 1958, Saul Kripke suggested the use of branching time in temporal logic. In this paper, however, it is argued that Prior worked with an idea close to the notion of branching time (‘the big Y’) already the year before he received Kripke’s letter. It is likely that Prior’s findings based on this e...

The logic and philosophy of William of Ockham (ca. 1285–1347) was a very important inspiration to the founding father of modern tense-logic, A. N. Prior (1914–69). This paper offers a discussion of four aspects of the Ockhamistic inspiration in modern tense-logic: (1) the criticism of the analysis of future contingents in terms of three-valued logi...

This paper describes a study of the development and use of e-learning tools in the context of a basic logic course that was taught during the COVID-19 lockdown in 2021. The tools were used to compensate for learning and teaching limitations brought about by the lockdown. We compare a course that was taught in February and March 2020 (before the loc...

This paper is a study of the use of e-learning tools and log data in evaluating and further developing a course on basic logic. It is a continuation of earlier studies involving practical experiments with students of communication from Aalborg University. Two tools are involved: Syllog for training syllogistic reasoning and Proplog for training bas...

This paper is a study of the use of E-learning tools in a course on basic logic. It is a continuation of earlier studies involving practical experiments with students of communication using the Syllog system for syllogistic reasoning. In the present study, we also discuss the use of the Proplog system which we developed to support a part of the cou...

This paper is a critical discussion of A.N. Prior’s contribution to the modern understanding of indeterminism and human freedom of choice. Prior suggested that these ideas should be conceived in terms of his tense logic. It can be demonstrated that his approach provides an attractive formalization that makes it possible to discuss indeterminism and...

Abstract: Arthur Norman Prior (1914-69) was a logician and philosopher from New Zealand who contributed crucially to the development of ‘non-standard’ logics, especially of the modal variety. His greatest achievement was the invention of modern temporal logic, worked out in close connection with modal logic. However, his work in logic had a much br...

In his philosophy, William of Ockham (1285-1347) offered an important and detailed response to the classical argument from the truth of a statement regarding the future to the necessity (unpreventability) of the statement. In this paper, Ockham's solution and the possible formalisation of it are discussed in terms of modern tense and modal logic. I...

The founding father of modern temporal logic, A.N. Prior, held that there is a logical tension between the Christian doctrines of human freedom and divine foreknowledge. He argued that future contingents cannot be true now, since there is no way to settle them now. In consequence, he found that the classical doctrine of divine foreknowledge has to...

Thoughts on Time, Truth, and Transcendence Abstract. The founding father of modern temporal logic, A.N. Prior, held that there is a logical tension between the Christian doctrines of human freedom and divine foreknowledge. He argued that future contingents cannot be true now, since there is no way to settle them now. In consequence, he found that...

Der kan næppe være nogen tvivl om, at Niels Bohrs overvejelser angående forholdet mellem subjekt og objekt hører til hans allervæsentligste bidrag til analysen af menneskets erkendelsessituation.

A. N. Prior very much admired the logic and philosophy of C.S. Peirce. In the spring of 1962 Prior went to Chicago to study Peirce's ideas. One of the topics that caught his attention was Peirce's existential graphs. This interest continued when he returned to England. In this paper Prior's grappling with the existential graphs will be discussed.

This paper is a study of various strategies for teaching syllogistics as part of a course in basic logic. It is a continuation of earlier studies involving practical experiments with students of Communication using the Syllog system, which makes it possible to develop e-learning tools and to do learning analytics based on log-data. The aim of the p...

This paper is a study of various e-learning strategies for teaching basic ideas in logic. The focus is mainly on syllogistic validity and deduction. It is a continuation of earlier studies involving practical experiments with students of Communication using the Syllog system, which makes it possible to develop e-learning tools and to do learning an...

A.N. Prior’s Past, Present and Future [18] was published 50 years ago in 1967 and was clearly a milestone in the development of tense-logic. It is a mature and comprehensive presentation of the basic concepts, systems and issues in tense-logic. In addition it also contains a number of interesting ideas that later led to important further developmen...

A. N. Prior’s writings should obviously be studied already for historical reasons. His inventions of modern temporal logic and hybrid logic are clearly important events in the history of logic. But the enduring importance of studying his works also rests on his methodological approach, which remains highly relevant also for systematical reasons. In...

Logic has sometimes been seen as an alternative to metaphysics and to speculation. In this paper it is argued that a different story should be told when it comes to temporal logic and tense-logic in particular. A. N. Prior's first formulation of tense logic was mainly established in order to qualify the discussion of certain metaphysical and concep...

The use of branching time diagrams in tense logic was originally suggested in 1957 by Saul Kripke. During the following years, A.N. Prior (1914–1969) developed models with forwards branching and backwards linearity. Prior’s work on tense logic inspired several logicians during the 1960s, such as Nino Cochiarella (born 1933) and Henrik von Wright (1...

This paper offers a discussion of the usefulness of the ontology editor Protégé 5.0 as a tool for working with qualitative data. As an illustration we focus on an ongoing research project on the worldviews and beliefs of three groups of religious and spiritual professionals in Denmark. It is argued that the use of Protégé in this case can provide i...

As pointed out by St. Augustine we cannot give a proper definition of time as such. Furthermore, conceiving time as a literal object would be highly problematic. It is, however, possible to establish a conceptual framework for meaningful discussion of the temporal aspects of reality in terms of the philosophical logic of time developed by Arthur No...

This paper is a continuation of earlier studies involving experiments with Communication students using a Java-Applet running in the student’s browser, developed using the Prolog programming language as embodied in a Java implementation called Prolog+CG. This makes it possible to support logic teaching through the use of interactive systems and als...

Purpose – The purpose of this paper is to explore artificial moral agency by reflecting upon the possibility of a Moral Turing Test (MTT) and whether its lack of focus on interiority, i.e. its behaviouristic foundation, counts as an obstacle to establishing such a test to judge the performance of an Artificial Moral Agent (AMA). Subsequently, to in...

It has for centuries been commonly believed that syllogistic reasoning is an essential part of human rationality. For this reason, Aristotelian syllogistics has since the rise of the European university been a standard component of logic teaching. During the medieval period syllogistic validity was presented in terms of a number of artificial words...

According to A. N. Prior the use of temporal logic makes it possible to obtain a clear understanding of the consequences of accepting the doctrines of indeterminism and free choice. Nuel Belnap is one of the most important writers who have contributed to the further exploration of the tense-logical systems as seen in the tradition after Prior. In s...

This paper focuses on the logical tense between two Christian doctrines which are considered to be fundamental, i.e. the doctrines of divine foreknowledge and human freedom, respectively. It has often been argued that the combination of these two doctrines gives rise to a logical contradiction, and that at least one of the two doctrines therefore h...

In this paper the focus is on the construction, use, pedagogical potential, and long-term sustainability of certain web-based tools designed for teaching logic. A series of web-based tools have been implemented as a two-part system, and the tools have been tested and evaluated in a number of practical experiments. The first part of the system is a...

This paper presents some of the initial steps taken towards digital mediation of the cultural heritage related to Danish author Kaj Munk and the impact these steps have had on the ongoing research on persuasive learning.

The concept of persuasive design has demonstrated its benefits by changing human behavior in certain situations, but in the area of education and learning, this approach has rarely been used. To change this and to study the feasibility of persuasive technology in teaching and learning, the EuroPLOT project (PLOT = Persuasive Learning Objects and Te...

The EuroPLOT project 2010-2013 has developed Persuasive Learning and Technologies PLOTs and has evaluated them in four real-world case studies, which cover the widely different teaching scenarios of university education, adult learning in industry, informal learning at a museum, literature studies, and language learning. At the International Worksh...

Today, many would assume that Charles Darwin absolutely rejected any claim of intelligent design in nature. However, review of his initial writings reveals that Darwin accepted some aspects of this view. His conceptualization of design was founded on both the cosmological and the teleological ideas from classical natural theology. When Darwin disco...

This paper focuses on the challenges of introducing classical syllogisms in university courses in elementary logic and human reasoning. Using a program written in Prolog+CG, some empirical studies have been carried out involving three groups of students in Denmark; one group of philosophy students and two groups of students of informatics. The skil...

In his paper, The logic of obligation and the obligations of the logician, A.N. Prior considers Hintikka’s theorem, according to which a statement cannot be both impossible and permissible. This theorem has been seen as problematic for the very idea of a logic of obligation. However, Prior rejects the view that the logic of obligation cannot be for...

The HANDS project suggests the use of Mobile Persuasion in order to support teenagers with an autism diagnosis and normal or high IQ. The paper offers a description of the HANDS toolset and its potential. The HANDS toolset has been evaluated at four schools for teenagers with autism over a period of 7 months. The paper presents the main conclusions...

This paper deals with the historical and philosophical background of the introduction of the notion of branching time in philosophical logic as it is revealed in the hitherto unpublished mail-correspondence between Saul Kripke and A.N. Prior in the late 1950s. The paper reveals that the idea was first suggested by Saul Kripke in a letter to A.N. Pr...

Purpose Helping Autism‐diagnosed teenagers navigate and develop socially (HANDS) is an EU research project in progress. The aim of HANDS is to investigate the potential of persuasive technology as a tool to help young people diagnosed, to whatever degree, as autistic. The HANDS project set out to develop mobile ICT solutions to help young people wi...

This paper deals with the historical and philosophical background of the introduction of the notion of branching time in philosophical logic as it is revealed in the hitherto unpublished mail-correspondence between Saul Kripke and A.N. Prior in the late 1950s. The paper reveals that the idea was first suggested by Saul Kripke in a letter to A.N. Pr...

Some very good arguments can be given in favor of the Augustinean wisdom, according to which it is impossible to provide a satisfactory definition of the concept of time. However, even in the absence of a proper definition, it is possible to deal with conceptual problems regarding time. It can be done in terms of analogies and metaphors. In particu...

A.N. Prior's work with Peirce's philosophy and investigations into the formalisation of temporal ontology give rise to some important questions regarding time and existence. Some answers to these questions are considered in this paper, which deals mainly with A.N. Prior's ideas on time and existence. The focus is on Prior's analysis of problems con...

The HANDS (Helping Autism-diagnosed teenagers Navigate and Develop Socially) research project involves the creation of an e-learning toolset that can be used to develop individualized tools to support the social development of teenagers with an autism diagnosis. The e-learning toolset is based on ideas from persuasive technology. This paper address...

This paper deals with the history and the philosophy of some important conceptual structures of time and modality. In particular, the focus is on the historical and philosophical background of the introduction of the notion of branching time as a useful conceptual structure in philosophical logic. It is pointed out that the idea was first suggested...

The 18th International Conference on Conceptual Structures (ICCS 2010) is the latest in a series of annual conferences that have been held in Europe, Australia, and North America since 1993. Conceptual structures (CS) recognise that organisations work with concepts; machines like structures. The objective driving research and development on CS...

Time is not definable in terms of other concepts. On the other hand, it is generally accepted that Augustine was right in claiming that we as human beings have a tacit knowledge of what time is. But how can this tacit knowledge be explored and discussed, if time as such cannot be defined? This paper suggests that temporal logic, and in particular t...

The word 'ontology' was constructed at the outset of the seventeenth century by Jacob Lorhard (1561-1609). In this paper, it is argued that Jacob Lorhard's work on ontology should be regarded as an important resource, not only for professional historians of science, but also for researchers working within the field of formal ontology and its use fo...

This paper deals with A.N. Prior’s analysis of the concepts of dynamic and static time, i.e., McTaggart’s so-called A- and B-concepts. The relations and mutual dependencies between these temporal concepts are investigated, and Prior’s response to McTaggart’s views is discussed. Furthermore, Prior’s notion of branching time is analysed. It is argued...

The HANDS project is designed for Helping Autism-diagnosed Navigate and Develop Socially (HANDS) and combines studies within the pedagogical and psychological fields with the more technological field of Persuasive Design (PD). Functional deficits in social ability are considered in teenagers with Autism Spectrum Disorder (ASD) in relation to underl...

This paper deals with A.N. Prior's Ockhamism and "the true futurist theory". The introduction contains an outline of the historical background of the theories mainly in medieval theology and logic. In section 2, a formal version of the medieval argument for determinism will be presented without theological references. It will be pointed out that th...

The project, HANDS (Helping Autism-diagnosed teenagers Navigate and Develop Socially), studies how teenagers with ASD and with IQ within the normal range (IQ > 70) can handle what they see as difficult situations using mobile technology. HANDS is a project sponsored by the European Commission as part of the 7th Framework Programme. It is the basic...

Jacob Lorhard published his ontology in 1606. In this work the term ontologia ‘ontology’ was used for the first time ever. In this paper, it is argued that Lorhard’s ontology provides a useful key to the understanding of the early 17th-century world view in Protestant Europe. Among other things, Lorhard’s ontology reflects how the relations between...

A growing number of information technology systems and services are being developed to change users' attitudes or behavior or both. Despite the fact that attitudinal theories from social psychology have been quite extensively applied to the study of user intentions and behavior, these theories have basically provided checklists or rules of thumb ra...

In this paper, we describe a software system for learning graph-based reasoning. The system is designed for learning Peircean graphs in an interactive fashion that allows each student to proceed in his or her own pace. The student may use the built-in exercise library working from easy exercises towards harder ones, or may work at exercises of his...

Abstract. During the Renaissance there was a growing interest for the use of diagrams within conceptual studies. This paper investigates the historical and philosophical foundation of this renewed use of diagrams in ontology as well as the modern relevance of this foundation. We discuss the historical and philosophical background for Jacob Lorhard’...

The surveillance in public and private places, both physically and digitally, is increasing for different reasons. In this paper we intend to discuss surveillance and persuasive technology in an ethical perspective with an eye to its historical and cultural context. In section 1, we present some different tendencies of surveillance in society. In s...

This paper deals with certain ethical problems inherent in psychological research based on internet communication as stored information. Section 1 contains an analysis of research on Internet debates. In particular, it takes into account a famous example of deception for psychology research purposes. In section 2, the focus is on research on person...

This chapter discusses the continuous work in modern temporal logic, focusing on the philosophical problems that originally inspired Arthur Norman Prior in his pioneering work within temporal logic. The chapter focuses on the philosophical motivation and the various conceptual aspects of the formalisms of modern temporal logic. Construed in this ma...

This chapter presents a brief biography of Arthur Norman Prior with particular focuses on his logic. Arthur Norman Prior was born on December 4th, 1914 in Masterton in the North Island of New Zealand. The chapter focuses on main trends in Prior's philosophical logic: (1) the logic of ethics, (2) how temporal logic began: human freedom and divine fo...

Ontology as the study of being as such dates back to ancient Greek philosophy, but the term itself was coined in the early 17th century. The idea termed in this manner was further studied within academic circles of the Protestant Enlightenment. In this tradition it was generally believed that ontology is supposed to make true statements about the c...

Any non-trivial top-level ontology should take temporal notions into account. The details of how this should be done, however, are frequently de- bated. In this paper it is argued that "the four grades of tense-logical involve- ment" suggested by A.N. Prior form a useful framework for discussing how various temporal notions are related in a top-lev...

In this paper we investigate principles of the representation of time and modality in terms of conceptual graphs. Based on the works of A. N. Prior, and C. S. Peirce, we suggest a formalism that takes into account the notion of 'Now', as a starting point for developing a formalism that can account for comprehension of texts involving temporal descr...

This is a revised and expanded edition of a seminal work in the logic and philosophy of time, originally published in 1968. Arthur N. Prior (1914-1969) was the founding father of temporal logic, and his book offers an excellent introduction to the fundamental questions in the field. Several important papers have been added to the original selection...

In this paper we describe and evaluate two on-line courses on Conceptual Graphs and Prolog+CG given to 2nd and 3rd year students of Humanistic Informatics at Aalborg University, Denmark. The average student had no prior experience with formal languages, nor did they have any advanced mathematical background, but nevertheless they succeeded in achie...

In the study of interactive multimedia systems we are obviously dealing with temporal series or structures of events. It seems natural to make a distinction between two kinds of series of events which are relevant for the study of interactive multimedia systems. Firstly, the user’s interaction with the system itself constitutes a series of events,...