Online research in philosophy

At the beginning of the Posterior Analytics, Aristotle says that “all learning and all rational teaching arises from previously existing knowledge”. How, then, can we have any knowledge? If all our knowledge is acquired by learning that depends on previously existing knowledge, then we would have an infinite regress of still prior knowledge, with the result that we cannot learn anything without having learned something else first. If we reject this possibility, then the only one that remains is that we have some knowledge that we did not learn. This might happen in two ways: either we have some knowledge that we never acquired at all, or we have some knowledge that we acquired but without learning it. We would have knowledge that we never acquired if there was never a time at which we did not have it (which would entail, of course, that we were born with it). Plato held that we do have such knowledge, and indeed that all the genuine knowledge that we have is innate in this way. Aristotle, however, denies that we have innate knowledge (for instance at An. Post. II.19, 100a10). Since he nevertheless does think that we have knowledge, he must think that we have some knowledge which we did not acquire by learning. In fact, he does present such a view in Posterior Analytics II.19, where he claims that our knowledge of the principles ( ¢¡¤£¦¥¨§ ) of sciences comes to us through perception and induction and that the state of knowledge of them is “intelligence” or “thought” ( © ). Aristotle says explicitly that in this process the mind is passive; therefore, it is reasonable for us to regard it as not being a kind of learning (or at any rate as a kind of rational learning). Thus, Aristotle’s overall position is consistent.

In the Posterior Analytics, Aristotle takes up the position of those who hold that all knowledge is demonstrable, and, hence, scientific. Such people are said to base their arguments on the fact that some demonstrations are circular or reciprocal (72b251). As Aristotle makes clear in the text, a circular demonstration consists of an argument (form) in which the conclusion is equivalent to one of the premises. But as Aristotle hastens to point out, demonstrations cannot be circular, for the essence of demonstration is to proceed from what is prior to what is posterior, and the same things cannot be both prior and posterior. A circular demonstration has the form ‘if A is, then B must be;’ and ‘if B is, then A must be’: “consequently, the upholders of circular demonstration are in the position of saying that if A is, A must be—a simple way of proving anything” (73a5).

The aim of this article is to help to clarify the role which Aristotle gives to definition in his theory of demonstration. I shall begin by examining his handling of the relations between definition and demonstration in chapters 8-10 of the second book of the Posterior Analytics, in order to provide an outline for an interpretation of Aristotle's thought. Secondly, I shall examine chapter 10 in more detail, bringing out the contrast between the commentary by Averroes and that of Grosseteste. I have chosen these two commentators because, both being generally magnificent interpreters of Aristotle, as far as the nature and types of definition are concerned their understanding of Aristotle is strikingly different.

During the Middle Ages and Rennaissance, it was commonly believed that Aristotle's biological studies reflected his theory of demonstrative science quite well. By contrast, most commentators in the twentieth century have taken it that this is not the case. This is largely the result of preconceptions about what a natural science modelled after the proposals of Aristotle's Posterior Analytics would look like. I argue that these modern preconceptions are incorrect, and that, while the Analytics leaves a variety of issues unanswered that a practicing biology must have answers to (hence Parts of Animals I), Aristotle's biological practice conforms to the Analytics model. It is further argued that establishing this claim requires reading philosophically through entire biological treatises--that is, one will miss the logical structure by following the usual practice of 'sampling' these treatises rather than reading them systematically.

In Aristotle's teleological view of the world, natural things come to be and are present for the sake of some function or end (for example, wings are present in birds for the sake of flying). Whereas much of recent scholarship has focused on uncovering the (meta-)physical underpinnings of Aristotle's teleology and its contrasts with his notions of chance and necessity, this book examines Aristotle's use of the theory of natural teleology in producing explanations of natural phenomena. Close analyses of Aristotle's natural treatises and his Posterior Analytics show what methods are used for the discovery of functions or ends that figure in teleological explanations, how these explanations are structured, and how well they work in making sense of phenomena. The book will be valuable for all who are interested in Aristotle's natural science, his philosophy of science, and his biology.

In an earlier article (s. J Gen Philos Sci 40:341–355, 2009), I have rejected an interpretation of Aristotle’s syllogistic which (since Patzig) is predominant in the literature on Aristotle, but wrong in my view. According to this interpretation, the distinguishing feature of perfect syllogisms is their being evident. Theodor Ebert has attempted to defend this interpretation by means of objections (s. J Gen Philos Sci 40:357–365, 2009) which I will try to refute in part [1] of the following article. I want to show that (1) according to Aristotle’s Prior Analytics perfect and imperfect syllogisms do not differ by their being evident, but by the reason for their being evident, (2) Aristotle uses the same words to denote proofs of the validity of perfect and imperfect syllogisms („ apodeixis “, “ deiknusthai ” etc.), (3) accordingly, Aristotle defines perfect syllogisms not as being evident, but as “requiring nothing beyond the things taken in order to make the necessity evident“, i.e. as not “requiring one or more things that are necessary because of the terms assumed, but that have not been taken among the propositions” ( APr. I. 1), (4) the proofs by which the validity of perfect assertoric syllogisms can be shown according to APr. I. 4 are based on the Dictum de omni et nullo , (5) the fact that Aristotle describes these proofs only in rough outlines corresponds to the fact that his proofs of the validity of other fundamental rules are likewise produced in rough outlines, e.g . his proof of the validity of conversio simplex in APr. I. 2, which usually has been misunderstood (also by Ebert): (6) Aristotle does not prove the convertibility of E -sentences by presupposing the convertibility of I -sentences; only the reverse is true.