This paper concerns Aristotle's kind‐crossing prohibition. My aim is twofold. I argue that the traditional accounts of the prohibition are subject to serious internal difficulties and should be questioned. According to these accounts, Aristotle's prohibition is based on the individuation of scientific disciplines and the general kind that a discipline is about, and it says that scientific demonstrations must not cross from one discipline, and corresponding kind, to another. I propose a very different account of the prohibition. The prohibition is based on Aristotle's scientific and metaphysical essentialism, according to which a scientific demonstration must take as its starting point a set of per se properties of a subject, if these make up a single, unitary definition. The subject of demonstration here is a kind, although not the general kind associated with a discipline, but rather the particular kind that the particular demonstration is about.

This paper sets out to evaluate the claim that Aristotle's Assertoric Syllogistic is a relevance logic or shows significant similarities with it. I prepare the grounds for a meaningful comparison by extracting the notion of relevance employed in the most influential work on modern relevance logic, Anderson and Belnap's Entailment. This notion is characterized by two conditions imposed on the concept of validity: first, that some meaning content is shared between the premises and the conclusion, and second, that the premises of a proof are actually used to derive the conclusion. Turning to Aristotle's Prior Analytics, I argue that there is evidence that Aristotle's Assertoric Syllogistic satisfies both conditions. Moreover, Aristotle at one point explicitly addresses the potential harmfulness of syllogisms with unused premises. Here, I argue that Aristotle's analysis allows for a rejection of such syllogisms on formal grounds established in the foregoing parts of the Prior Analytics. In a final section I consider the view that Aristotle distinguished between validity on the one hand and syllogistic validity on the other. Following this line of reasoning, Aristotle's logic might not be a relevance logic, since relevance is part of syllogistic validity and not, as modern relevance logic demands, of general validity. I argue that the reasons to reject this view are more compelling than the reasons to accept it and that we can, cautiously, uphold the result that Aristotle's logic is a relevance logic.

There is a variety of interpretations of how, in Metaphysics Gamma 2, Aristotle argues for the possibility of a science of the essence of being-of what being is; of being qua being-and does so, famously, by introducing the claim that this kind, being, exhibits a πρὸς ἕν structure; that is, the claim that the different kinds of being are essentially dependent on a single kind that is primary. It appears that the several interpretations come in three main varieties. First, there are those who, following Owen's classic article of 1960, argue that Aristotle's primary aim is to obviate the danger that the term 'being' is simply ambiguous, in the way in which the word 'bank' is in English and the word κάλυξ in Greek. 1 This, these critics think, is a real danger due to Aristotle's theory of categories, understood as the view that there are different ultimate kinds of being which do not fall under a single genus and which, for all that theory tells us, may or may not be essentially related. For it is obvious that if 'being' is ambiguous in this way, then there cannot be a science of the essence of being. Secondly, some critics, challenging Owen's view that the theory of categories represents such a danger and arguing that the πρὸς ἕν structure is present already in that theory, argue that Aristotle's aim, rather, is to show that the possibility of a science of a subject-matter does not require that the different kinds of the subject must belong to a single genus (the so-called καθ' ἕν structure) but is likewise provided for by a πρὸς ἕν structure. According to these critics, the need to show this is due to Aristotle's, in the Posterior Analytics, having accounted for the unity of a science entirely in terms of the strict genus-species relation (καθ' ἕν structure); so that his aim in the Metaphysics is, in effect, to relax the Posterior Analytics' requirements for the unity of a science. 2 Thirdly, other critics argue that the πρὸς ἕν structure, invoked for the purpose of unifying a science, is present already in the Posterior Analytics, and that the aim of the Metaphysics is to extend this mode of unification of a science from the special sciences to the general science of being. 3 Our question in the present paper is this: Does Aristotle, in Metaphysics Gamma 2, think that the claim that being exhibits a category-based πρὸς ἕν structure is also sufficient to defend the possibility of a science of being qua being, or does he think that it is only necessary? 4 We

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At least since Socrates, philosophy has been understood as the desire for acquiring a special kind of knowledge, namely wisdom, a kind of knowledge that human beings ordinarily do not possess. According to ancient thinkers this desire may result from a variety of causes: wonder or astonishment, the bothersome or even painful realization that one lacks wisdom, or encountering certain hard perplexities or aporiai. As a result of this basic understanding of philosophy, Greek thinkers tended to regard philosophy as an activity of inquiry (zētēsis) rather than as a specific discipline. Discussions concerning the right manner of engaging in philosophical inquiry -what methodoi or routes of inquiry were best suited to lead one to wisdom -became an integral part of ancient philosophy, as did the question how such manners or modes of inquiry are related to, and differ from, other types of inquiry, for instance medical or mathematical.In this special issue of History of Philosophy & Logical Analysis, we wish to concentrate in particular on ancient modes of inquiry. 1 But, the reader may wonder, why do we talk about modes of inquiry, rather than methods? There are at least two reasons for this. First, the modern term 'method' gives connotations of something wider than inquiry: we talk of various methods for doing something, or for going about something, without thereby implying that we are directly engaged in inquiry into something. In another sense, however, method is narrower than inquiry; for a method proper prescribes in a strongly regulative way how to proceed in order to get from an initial state to another state. Whether there are any such prescriptions for philosophical inquiry is an open question, both now and in antiquity. Most ancient philosophers would agree, however, that there are, as it were, small-scale methods or techniques in philosophy, for instance the method or technique of disproving a claim by counterexample; and they would further agree that such methods play some role in inquiry. However, most real philosophical inquiries are far too complex to be carried out by relying on only one such method or technique. A proper method of philosophical inquiry would thus at least require a description of how these specific individual techniques can be combined. But even if no such largescale method can be discovered in philosophy, philosophical inquiry may still be possible and facilitated by certain modes or elements in a general account of such inquiry. This latter possibility is especially important for the sceptical school of the Pyrrhonists, who were keen on claiming that they were engaged in inquiry without subscribing to any of the various methodoi which had been developed up to this point, and, in fact, to any specific method of inquiry at all. It 1 In the past years, a number of seminal contributions in relation to inquiry in ancient philosophy have been published; see, for instance, Fine (2014), Politis (2015) or Karamanolis & Politis (2018).