Man is not only a political animal. He also has within his breast the desire to understand. And there is a serious question as to how man can both fulfill his nature as a political animal and fully satisfy his innate desire to understand. The conflict is one which takes time to develop. For to a certain extent the desire to understand helps man to live the life of an active citizen. For man comes to understand that the ethical life within society is a way to achieve genuine human happiness; and when man comes to understand what happiness is, he is more likely to achieve it. However, if man pursues his desire to understand to the full he will find himself drawn outside the ethical life. It seems that it is man's nature to transcend his nature. Man is by nature a political animal, but he is also an animal who by nature desires to understand the world. And in coming to understand the world, he will leave the ethical life behind. His nature will take him beyond (or outside) his natural life as a political animal.

How are we to understand such a paradoxical conception? One way is to investigate the structure of theoretical understanding. For if we grasp what the desire to understand is a desire for, we may be able to see how satisfying the desire – achieving theoretical understanding – takes one outside the ethical life in society.

Nature as an inner principle of change

If we are to understand what it is for man by nature to desire to understand, we must understand what it is for something to exist by nature (phusei). Aristotle begins Physics II by saying that existent things can be divided into those which exist by nature and those which exist from other causes. The Greek word which is translated as ‘cause’ does not mean cause in the modern sense: namely, an antecedent event sufficient to produce an effect. Rather, it means the basis or ground of something. Aristotle later says that we do not understand something until we know why it is what it is: and the cause gives us ‘the why.’ We shall discuss Aristotle's conception of cause later. For the moment, the important point is that Aristotle thinks that to say that something exists by nature is to cite its cause.

Aristotle thinks he can unproblematically identify the things that exist by nature. The paradigms are living organisms – animals and plants – but he also includes their parts and the ‘simple bodies’ – earth, air, fire, and water. The task, for Aristotle, is to find the characteristic feature which distinguishes natural items from everything else. ‘Each of them,’ he says, ‘has within itself a principle of change and rest.’ The ability to grow is obvious in plants and animals, and animals can move about their environment, but even the simple elements have tendencies to move in fixed directions.

Soul

Soul was traditionally thought to be a principle of living things. Soul was invoked above all, Aristotle says, to explain two remarkable features of animal life: the capacity for movement, and the capacity for cognition – perception and thinking. However, previous thinkers treated soul as an independent item, which they joined to a body without explaining how the two could be related. Aristotle thinks he can give an adequate account of soul and its relation to body by relying on his distinction between form and matter. He defines soul as ‘the form of a natural body having life potentially within it.’ Since the form of a living body is its nature, it turns out that soul is the nature of living things: the inner principle of change and rest.

Form is the actuality of a body, the matter a potentiality, so soul is the actuality of a living organism. However, Aristotle distinguishes different grades of actuality. Aristotle uses the distinction between having learned an organized body of knowledge (an epistēmē) and actually exercising that knowledge. It is fitting to think of one's knowledge as an actuality: for one has passed beyond the stage of merely being capable of learning, one has actually acquired the knowledge. There is nothing that is left which remains to be done in order to be able to exercise it at will. Nevertheless, this does not seem to be as high a level of actuality as the exercise of one's knowledge.

The point of the Nicomachean Ethics

One reason for going back to Aristotle's ethics is to study how profoundly different his ethical outlook is from our own. It is fair to say that we live today without a coherent and compelling morality. There are various moral strands which pull in various directions, but when pushed for a justification we find it hard to explain why we should hold the moral beliefs we do hold. Much of what constitutes the Western moral outlook is inherited from the Judaeo-Christian tradition, and if 300 years ago one were asked, for example, why you should do unto others as you would have them do unto you, one would have undoubtedly given a religious answer. In the past 300 years there has been a dramatic loss of confidence in the ability of religious belief to ground a moral outlook. In part this loss is due to a growing conviction that moral beliefs ought to be justifiable other than by appeal to divine authority: they ought to appear reasonable to a moral agent. But with the loss of confidence in religion's ability to ground morality, no other form of justification has come to take religion's place. There are other forms of justification, to be sure, but none commands universal or deep respect.

One way in which we differ from the Greek world in which Aristotle lived is that we place more emphasis on intention than on act.

I wrote this book as a way of saying goodbye. I first went to Cambridge on a Mellon Fellowship when I graduated from Yale in 1970, and with occasional excursions back to the United States I ended up staying there for almost twelve of the next fifteen years. Cambridge is in many ways my intellectual and emotional home: I had never seen before such a warm, supportive, yet challenging intellectual environment. Perhaps that is why I stayed so long. When I decided to return to the U.S. in 1985, I wanted somehow to mark, intellectually if not emotionally, the time I had spent in Cambridge. Most of my research on Aristotle was done while I was first a student and later a Fellow at Clare College, so I decided to write an introduction to his philosophy. I liked the idea of an introduction, first, because I thought it would force me to work on a broad canvas: to elucidate the thoughts of years rather than detail a single argument. Second, I wanted to write a book that was accessible to my friends who are not Aristotelian scholars – friends who would ask me in countless casual conversations, ‘What do you think Aristotle would have thought about this?’ I am not going to mention my many Cambridge friends by name: if you are one of them and are reading this, suffice it to say that you are very much in my heart and mind.

This second volume of The Hellenistic Philosophers is strictly ancillary to the translations and commentaries which appear in vol. 1. Whereas vol. 1 is designed to be usable on its own, vol. 2 provides the sort of supplementary information required by readers familiar with Greek and Latin. It is not designed to be read in isolation.

The principal object of vol. 2 is to supply the originals of the texts which are translated in vol. 1. These are sometimes presented here in longer excerpts than appear in vol. 1, and in such cases the additional portions are marked by smaller print. Occasionally an entire extra text is added, also in smaller print, and designated with a lower case (instead of the usual upper case) bold letter.

The texts are accompanied by notes. These do not attempt systematic or exhaustive commentary, but offer cross-references, information on context and on further relevant texts, and discussion of obscure or controversial points of interpretation, particularly where this is required in order to justify the translations and interpretations proposed in vol. 1. If our coverage at times seems uneven, that is because we have found that some texts demand extensive elucidation, while others seem able to speak adequately for themselves.

We have not, with one or two special exceptions, attempted to obtain readings of the original manuscripts, but have relied principally on a standard edition of each work. These editions are listed in the Index of sources appended to vol. 1.

Introduction

The biological writings constitute over 25% of the surviving Aristotelian corpus. There are, first of all, the ‘big three’: Parts of Animals, Generation of Animals, History of Animals (usually referred to here by its Latin name, Historia Animalium). These comprise, respectively, some 58, 74, and 146 Bekker pages.

Then there are the smaller works, really monographs or even papers: Progression of Animals (De Incessu Animalium), 10 pages; Motion of Animals (De Motu Animalium), 7 pages; and the essays collected as Parva Naturalia, the ‘little nature studies’, of which the last two are especially ‘biological’: On Length and Shortness of Life, 3 pages; On Youth and Old Age, Life and Death, and Respiration, 13 pages. (Resp. is sometimes treated as a separate work.) Other essays in PN have a clearly biological element, especially On Sleep and Waking, though scholars have tended to treat them only as ‘psychology’, placing them rather with the De Anima than with the biology. De Anima itself is something of a bridge between the biology and the more familiar treatises such as the Metaphysics and the Ethics, and though it certainly belongs with the latter so far as amount of study received is concerned, it was at some point probably intended to provide a theoretical framework for the biological studies.

The following is taken from an extended work on Aristotle's theory of material substances that is forthcoming from Cambridge University Press. The course of developments leading up to the present extract is, briefly and roughly, as follows. Part I of the work (§§1–5) deals with the metaphysical theory of substance in the Categories, which is a considerably simplified and scaled-down version of the complete theory as found in various other writings of Aristotle. The most considerable simplifications are (1) the total absence of the notion of matter (8a9–11) is of no theoretical significance), and (2) a certain lack of explicitness as to whether the eidos (in the Categories, usually Englished as ‘species’) of a substantial individual is something essential to that individual, so that anything describable as its ceasing to have or belong in that eidos is tantamount to that individual's ceasing to exist. The question then naturally arises why these features of the full theory, as usually interpreted, should be thus effaced in the Categories version, if, as seems to me highly probable, the Categories is an authentic and mature Aristotelian work; and some suggestions are hazarded along these lines.

Part II (§§6–5) is a ‘first approximation’ of the complete theory of substance, necessarily somewhat attenuated and abstract in the absence of a rich intuitive conception of what a ‘full’ substance actually is – something that the Categories cannot possibly furnish.

Aristotle's teleology is a central component of his philosophy, and interpretations of it often heavily influence evaluations of the significance of his thought, both in science and in philosophy. Much has been written about this aspect of his philosophy, but surprisingly little sustained attention has been directed to what is clearly the fundamental question: what, precisely, does Aristotle mean when he asserts that something is, or comes to he, for the sake of something?

If we are to answer this question with both historical accuracy and philosophical precision, how must we proceed?

The place to begin, of course, is with the text – ideally, with Aristotle's own statement of an answer. One would expect to find, somewhere in the vast Aristotelian corpus, a thorough analysis and explicit definition of this central notion. Surprisingly, it is not there to be found. Readers of the corpus will search in vain for a detailed analysis of what it is to be (or come to be) for the sake of something.

The longest continuous passages on final causality, Physics 11.8 and (sections of) Parts of Animals 1.1, while containing much that eventually proves helpful, do not address themselves directly to this issue. In each case, the purpose is to argue for the applicability to nature of a conception of final causality whose precise meaning and statement is largely taken for granted.

The reform of diairesis

Aristotle's comments on logical division (diairesis) evidently refer to a more regular method than the examples given in Plato's late dialogues, but unfortunately no reliable evidence survives of Academic practice between the dialogues and Aristotle's Topics. We cannot know how much of the rules that Aristotle lays down may represent a codification of existing methods, and how much is correction of them. It is clear, however, that the criticisms and rules, which he sets out with great profusion of detail in the Topics and Analytics, are intended to ensure a good method, not merely to demolish bad ones, so that the picture which they build up may be taken as the form of diairesis of which he himself approved. It is very different from that set out by Plato, and the difference is exactly what we should expect after the change in philosophical viewpoint from Plato's theory of forms to Aristotle's theory of the substantial tode ti. Aristotle presents three major innovations: (i) the ontological distinctions between genus, differentia, species, property, essential and inessential accident, and other formal categories, which Plato did not distinguish; (ii) the insistence on successive differentiation, to preserve the unity of definition; (iii) division by a plurality of differentiae simultaneously, instead of by one at a time. These improvements are made respectively in (i) Topics and Categories; (ii) Posterior Analytics and Metaphysics; (iii) De Partibus Animalium 1.