Like Plato, Aristotle believed that we obtain all knowledge ultimately by an intuitive grasp of the essences of things. 'We can know a thing only by knowing its essence', Aristotle writes, and 'to know a thing is to know its essence'. A 'basic premiss' is, according to him, nothing but a statement describing the essence of a thing. But such a statement is just what he calls a definition. Thus all 'basic premisses of proofs' are definitions.
...Aristotle considers the term to be defined as a name of the essence of a thing, and the defining formula as the description of that essence. And he insists that the defining formula must give an exhaustive description of the essence or the essential properties of the thing in question; thus a statement like 'A puppy has four legs', although true, is not a satisfactory definition, since it does not exhaust what may be called the essence of puppiness, but holds true of a horse also; and similarly the statement 'A puppy is brown', although it may be true of some, is not true of all puppies; and it describes what is not an essential but merely an accidental property of the defined term.
But the most difficult question is how we can get hold of definitions or basic premisses, and make sure that they are correct - that we have not erred, not grasped the wrong essence. Although Aristotle is not very clear on this point, there can be little doubt that, in the main, he again follows Plato.... Aristotle's view is less radical and less inspired than Plato's, but in the end it amounts to the same. For although he teaches that we arrive at the definition only after we have made many observations, he admits that sense experience does not in itself grasp the universal essence, and that it cannot, therefore, fully determine a definition. Eventually he simply postulates that we possess an intellectual intuition, a mental or intellectual faculty which enables us unerringly to grasp the essences of things, and to know them. And he further assumes that if we know an essence intuitively, we must be capable of describing it and therefore of defining it. (His arguments in the Posterior Analytics in favour of this theory are surprisingly weak. They consist merely in pointing out that our knowledge of the basic premisses cannot be demonstrative, since this would lead to an infinite regress, and that the basic premisses must be at least as true and as certain as the conclusions based upon them. 'It follows from this', he writes, 'that there cannot be demonstrative knowledge of the primary premisses; and since nothing but intellectual intuition can be more true than demonstrative knowledge, it follows that it must be intellectual intuition that grasps the basic premisses.' In the De Anima, and in the theological part of the Metaphysics, we find more of an argument; for here we have a theory of intellectual intuition - that it comes into contact with its object, the essence, and that it even becomes one with its object. 'Actual knowledge is identical with its object.')
Summing up this brief analysis, we can give, I believe, a fair description of the Aristotelian ideal of perfect and complete knowledge if we say that he saw the ultimate aim of all inquiry in the compilation of an encyclopaedia containing the intuitive definitions of all essences, that is to say, their names together with their defining formulae; and that he considered the progress of knowledge as consisting in the gradual accumulation of such an encyclopaedia, in expanding it as well as in filling up the gaps in it and, of course, in the syllogistic derivation from it of 'the whole body of facts' which constitute demonstrative knowledge.
When it comes to essences and definitions, Rand generally follows Aristotle, although, here and there, she adds her own little wrinkles. Rand defines the "essence of a concept" as "that fundamental characteristic(s) of its units on which the greatest number of other characteristics depend, and which distinguishes these units from all other existents within the field of man's knowledge." [IOTE, 52] Here we find Rand echoing, in her own terms, Aristotle's distinction between essential and accidental properties. Rand also imagines knowledge as a kind of integrated encyclopedia cataloguing the entire "hierarchy" of knowledge:
Truth is the product of the recognition (i.e., identification) of the facts of reality. Man identifies and integrates the facts of reality by means of concepts. He retains concepts in his mind by means of definitions. He organizes concepts into propositions—and the truth or falsehood of his propositions rests, not only on their relation to the facts he asserts, but also on the truth or falsehood of the definitions of the concepts he uses to assert them, which rests on the truth or falsehood of his designations of essential characteristics. [IOTE, 48]And Rand concludes, ominously:
The truth or falsehood of all of man’s conclusions, inferences, thought and knowledge rests on the truth or falsehood of his definitions. [IOTE, 49]Where Rand appears to differ from Aristotle is when it comes to issue of how essences are discovered and identified. Rand rejects Aristotle's "intellectual intuition" in favor of what she calls "reason." While this "reason" always remains scandalously vague, Rand did provide a bit of hint on how one goes about discovering essential characteristics (i.e., essences):
Now observe . . . the process of determining an essential characteristic: the rule of fundamentality. When a given group of existents has more than one characteristic distinguishing it from other existents, man must observe the relationships among these various characteristics and discover the one on which all the others (or the greatest number of others) depend, i.e., the fundamental characteristic without which the others would not be possible. This fundamental characteristic is the essential distinguishing characteristic of the existents involved, and the proper defining characteristic of the concept.
This is as detailed an explanation that Rand ever bothered to provide on how to identify essences. For Rand, thinking in essentials involves observing relationships among various characteristics and discovering the one on which most of the others "depend." This dependence Rand describes as "the fundamental characteristic without which the others would not be possible." This, however, is an intolerably vague standard. Rand attempts to defend it by showing how the essence of man is discovered. Since "rationality," according to Rand, "explains" more characteristics of man than any other characteristic, rationality is therefore the essence of man. If this seems like special pleading, well, that is what it amounts to. It is not even clear that "rationality" would be the essence of man according to Rand's own theory of essence. There is a large body of evidence compiled by social thinkers like Pareto, by evolutionary psychologists like Steven Pinker, and by social psychologists like Jonathan Haidt which challenge the Rand's touching faith in man's rationality. But it hardly matters in any case. Rand's method of thinking in essentials is merely a rationalization of her own unique brand of rationalism. In practical terms, Rand's essentialism is merely thinking in terms of vague generalizations, which are arbitrarily regarded as "essential." It is the method of an inveterate rationalizer. It is not a method used in science or in any field of inquiry where truth takes precedence over ideology.
Leonard Peikoff, in his brief memoir "My Thirty Years with Ayn Rand," not only praises Rand for "thinking in essentials," but credits Aristotle for pioneering the intellectual tools required to develop this methodology:
The concept of "essential" was originated by Aristotle in connection with his theory of definitions. He used the term to name the quality that makes an entity the distinctive kind of entity thing it is, as against what he called "accidental" qualities. For example, having a rational faculty is essential to being a man. But having blue eyes rather than green is not; it is a mere detail or accident of a particular case. Ayn Rand's commitment to essentials grew out of this Aristotlean theory, although she modified the concept significantly and expanded its role in human thought.
For Ayn Rand, thinking in essentials was not restricted to the issue of definitions. It was a method of understanding any complex situation by deliberately setting aside irrelevancies — such as insignificant details, superficial similarities, unimportant differences — and going instead to the heart of the matter, to the aspects which, as we may say, constitute the distinctive core of the situation. This is something Ayn Rand herself did brilliantly. I always thought of her, metaphorically, as possessing a special power of vision, which could penetrate beneath the surface data that most people see, just as an X-ray machine penetrates beneath the flesh that meets our eyes to reveal the crucial underlying structures. [VOR, 342]
Two questions immediately arise from Peikoff's effusive praise. Peikoff describes Rand's "thinking in essentials" as "a special power of vision, which could penetrate beneath the surface data that most people see." What is the difference between this "special power" and Aristotle's "intellectual intuition"? Furthermore, if Rand was so brilliant at going "to the heart of the matter," why was she so wrong about human nature, the history of philosophy, and the role of ideas in history? Assuming that Rand did in fact follow some special method of thought derived from Aristotle (an assumption almost certainly false), we can only judge the efficacy of the method by the quality of its conclusions. We have extensively documented at ARCHN Rand's innumerable errors of logic and fact. If there was a method to all this madness it must be a very bad method. Thinking in essentials sounds great as a catch phrase. But no method of thought works well in practice unless its conclusions are rigorously criticized and tested by experience. Rand loathed criticism of her ideas and treated anyone who dared to challenge her with hostility and contempt. Her method of thinking in essentials could therefore only serve to confirm her errors; and that seems to be its main function in her philosophy.
Human nature and human society are two very complex realities. They cannot be mastered merely through "proper" concept formations, "proper" definitions, and thinking in terms of essentials and the "rule of fundamentality." They can only be mastered through extensive immersion in the subjects themselves, coupled with intense self and peer criticism. When going through Rand's writings on politics and psychology, one is constantly struck by the sheer ignorance of the woman. She often seems way out of her depth, not because of any lack of intelligence, but simply out of a lack of mastery of the subject at hand. Her essentialism consists in little more than ignoring inconvenient facts (e.g., the role of desire in human motivation) or concealing her ignorance in generalities (e.g., her remarks about Kant, Hume, Russell, etc.). She is too ignorant to even be aware of her ignorance; and therefore her writings suffer from what can only be described as deep rooted pretence of knowledge.