One of the first problems in discussing language development is to define what language is and what it is not. Of course, asking the question in this way is consistent with the common practice in psychology and philosophy of asking about the true nature of various human phenomena. For example, psychologists frequently ask whether some instance of behavior is truly language, or thinking, or a sign
... [Show full abstract] of intelligence, etc. Such questions are flawed because they are based on an essentialist approach to psychology (Palmer & Donahoe, 1992). With respect to behavior we call language, essentialism assumes, first, that there is a quality or essence that can be called language. One implication of this initial assumption is that this essence of language has an existence independent of the observed behavior. Once that assumption has been made, psychologists and philosophers begin looking for evidence of the presence of language. Following from the philosophical (i.e., Cartesian) traditions of psychology, essentialist scholars assume that the true essence of language is located somewhere in the mind. Unfortunately, because mental events are always inferred and never independently observed, psychologists must find other evidence for their existence. The only evidence for the existence of essentialist qualities in the mind is the behavior of individuals.