Aristotle Posterior Analytics – Lecture III Today’s Class • Post. An. Book II • Deﬁnitions • Essences • Grasp of First Principles Book II • Opens with an account of deﬁnition • Aristotle’s science is an attempt to discover the real natures of kinds • An Aristotelian deﬁnition gives us an account of each of these kinds • Aristotelian deﬁnitions are objective, not stipulative or conventional Four Questions • When we ask about anything, there are four kinds of question we can ask, corresponding to four things we can know 1. The “that” (ὅτι) e.g. “Is it so that A is B” 2. The “why” (διότι) e.g. “Why is A B” 3. If it is (εἰ ἔστι) e.g. “Does A exist” 4. What it is (τί ἔστι) e.g. “What is A”* * This is the “essence” of a thing. Essentia is the Latin term for Aristotle’s “What it is to be”. Aristotle’s Examples 1. Does the Sun suffer eclipse? (fact) 2. Why does the Sun suffer eclipse? (reason) 3. Do Centaurs or Gods exist? (existence) 4. What is a God? What is a man? (essence) Dependencies • To know why something happens, you must already know that it is the case. • e.g. So to know why the Sun is eclipsed, you must ﬁrst know that it is in fact eclipsed. • Therefore: questions of type 2 depend on answers to questions of type 1 Similarly.... • Aristotle thinks that questions of type 4 are dependent on answers to questions of type 3. • e.g. we cannot know what a Centaur is (i.e. know the essence of Centaurs) unless Centaurs exist • But this is controversial What about Non-beings? • It seems that we can know what a unicorn is, or a dragon, or even a dinosaur, without these things existing (some of them have never existed). • Moreover, compare Socrates in some of Plato’s dialogues, who thinks that we must know what X is before we can know that X exists. • In other words: how can you answer the question of whether zebras exist, if you don’t know what zebras are? • If I didn’t know what zebras were, I would walk around forever trying to ﬁnd them. I would even walk right past them, because I don’t know what it is to be a zebra. • So how could I ever start? Aristotle’s Answer • If I ask you to ﬁnd a zebra, you may ask me what I mean by “zebra”. • So I say “A stripey donkey” • That is sufﬁcient for you to ﬁnd zebras if they exist • But it is not the essence of being a zebra • In other words, our ordinary descriptive deﬁnitions of things may not be the same as essences. • Our meanings are not the same as Aristotelian essences. • Our meanings are conventional or stipulative, whereas Aristotelian essences exist independently of our thought or speech • I may ﬁnd a zebra due to the description you give me, and when I do ﬁnd it, I can try to determine the essence of a thing. • e.g.You could tell me to look for things “like this” when you point to a triangle, but that does not tell me the essence of a triangle. • I can come to know the essence of triangles through the clearly known particular (induction to the universal). Therefore... • Aristotle is right. Questions about the essence of things clearly require the existence of those things, since essences are objective. • This also counts for formerly existent things like dinosaurs. There is such a thing as “what it is to be” a dinosaur, only if dinosaurs actually existed. Deﬁnition (ὁρισμὸς) • An Aristotelian deﬁnition states the essence of a thing (sometimes called the “formula”). • e.g. Man = rational animal • To give the essence of a thing (i.e. a species), you need to give its genus and differentia. • Animal = the genus; Rational = the differentia • An Aristotelian deﬁnition looks like a dictionary deﬁnition • But it expresses the nature of a real objective kind • Dictionary deﬁnitions need not (e.g. unicorns, dragons, etc.) • Dictionary deﬁnitions can be wrong, but Aristotelian deﬁnitions must hold of their subject to be deﬁnitions at all Cause and Essence • Aristotle: the cause of something is the same as its essence • e.g. an eclipse • The essence of an eclipse is the obstruction of light by a heavenly body • Eclipses happen because heaven bodies obstruct light (cause) • Why are whales warm blooded? • Because they are mammals (commensurate universal) • But the essence of being a mammal is to be a warm blooded animal • So the essence supplies the cause Another Example • Question: “What is a concord?” (essence question) • Answer: “A concord is a numerical ratio of high and low pitch” (essence) • Question: “Why is the high note concordant with the low?” (causal question) • Answer: “Because it has a numerical ratio” Aristotle’s Science • Aristotle assumes that the fact that whales are warm blooded is a necessary feature of the world (it could not have been otherwise) • But we might think that this is just a contingent feature of reality • e.g. Necessity must be a priori (there are no a posteriori necessities) Against Aristotle • Modern Empiricist philosophers (from Locke and Hume onwards) insisted that the only necessities are those yielded by Analytic Truths. • Early 20th century Analytical Philosophers (such as the Logical Postivists) accepted this view. • There are no empirical necessities, only logical (analytic) necessities Frege & Russell • Both Frege and Russell were interested in the question of how names have meaning. • Both rejected the view that the meaning of a name is its referent • Frege divided meaning into Sense and Reference • Russell argued that names were disguised descriptions Why? • Because if meaning is just reference, then “The Morning Star” and “The Evening Star” have the same meaning, because each refers to the same thing (the planet Venus). • But someone could believe that the Evening Star is different from the Morning Star • How could they believe this if the terms have the same meaning? • It would be like someone believing that the Morning Star is not the Morning Star, which is a contradiction. The Frege/Russell Solution • We must distinguish between the referent and the way in which a word presents the referent. • e.g. “The Morning Star” and “The Evening Star” present the referent under different aspects. • Frege claimed that although these terms have the same reference, they have a different sense. • So although Clark Kent is identical with Superman, Lois Lane can believe that Clark Kent is not Superman, since the sense of “Clark Kent” is different than the sense of “Superman”. • Senses are different ways of “having things in mind”. • What we would call “sameness of meaning” is really sameness of sense. • Russell’s view is that names are disguised descriptions. • A Russellian description serves the same function as a sense (e.g. the star that appears in the morning) Analyticity • On this view, necessity is a matter of analyticity • Analytic truth = truth by virtue of meaning • So “All triangles are three sided ﬁgures” is necessarily true because “triangle” and “three sided ﬁgure” have the same meaning. • Analytic truths are true by deﬁnition. • They are also all a priori statements (statements that are true no matter what is true in the world) But... • “Water is H O” is not a necessary truth, 2 because the terms have different senses. • Someone could believe that water is not H2O without believing that water is not water (there is no contradiction here). • An Aristotelian would argue that “Water is H2O” is a necessary truth, because this is the essence of water (what water is). • Similarly, an Aristotelian would argue that it is essential (i.e. necessary) to being a pig, that pigs cannot ﬂy. • But on the Frege/Russell view, “Pigs cannot ﬂy” is not a necessary truth, because it is not analytic. • On this view “pigs cannot ﬂy” is a contingent statement, because someone who says they can is not involved in a contradiction Putnam & Kripke • One consequence of the Frege/Russell view is that there are no empirical necessities (statements about the world are not necessary truths – all necessity is a priori) • In the late 20th century, some philosophers argued that this cannot be right. • Saul Kripke and Hilary Putnam authored the most famous arguments. Hilary Putnam • Putnam argues that deﬁnitions cannot be “in the head” • e.g. Take two planets “Earth” and “Twin Earth”, which look alike to all observers • But even though it looks the same, what we call “water” on earth has a different chemical composition (H2O) to “water on twin earth (XYZ). • If we assumed that meaning was “in our heads”, then “water” would mean the same thing on earth and twin earth. • But it doesn’t, since our “water” means H O 2 and their “water” means XYZ. • So what we really mean when we use the word “water” is the objective nature of the thing (even if we don’t know this) • This is similar to Aristotle’s view (cf. whales) Kripke • Kripke argued that statements like “Water is H2O” are necessary truths, even though they are not a priori. • If “Socrates” really means something like the description “the teacher of Plato” to a person (Russell), then they mean the same thing to that person. • But what if Socrates had died young? That might have happened. • Then, if “the teacher of Plato” is synonymous with “Socrates”, someone else could have become Socrates. • But that is absurd, only Socrates was Socrates, whatever descriptions are true of him (or not). • Kripke: “Socrates” is a rigid designator • It is not logically possible for a rigid designator to refer to anything else (unlike non-rigid designators like “the teacher of Plato”) • So, on Kripke’s view, the way in which we think about things (sense) does not have anything to do with the meaning of names like “Socrates”. • Kripke: natural kind terms are rigid designators • “Water” and “H2O” refer to the same object in the world. Both designate rigidly. • Thus it could never be true that these terms referred to different entities. • So “Water is H2O” is necessarily true, (whether we know it or not) even though this is not an a priori truth (it is a truth about the world, not about our concepts) • This is pretty much the same as Aristotle’s view. Being H2O is the objective essence of water, and this is not changed by our use of words.
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