15 - T he general structure of the a rgument: a. There is...

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Unformatted text preview: T he general structure of the a rgument: a. There is knowledge. (implicit premise) b. Knowledge is of what is. (premise) c. Knowledge is infallible, belief is fallible. (premise) d. Therefore, what is known must be, what is believed may not be. e. That is, what is known is something that “purely and absolutely is,” what is believed is something that “partakes of both being and not-being.” f. Therefore, there are things that purely and absolutely are - t hings we call Forms ( the F I tself, etc.). The participants in the Forms (the many F s, etc.) both are and are not. g. That is, Forms are the objects of knowledge; their participants are objects of belief. I nterpreting the a rgument a. Plato’s three claims: ( K) Knowledge is of w hat is. (477a1) ( I) Ignorance is of w hat is not . (477a3) ( B) Belief is of w hat is and is not . (477a-b) b. What is the sense of “is” (“be”) involved? o o o is e: existential is p: predicative is v: veridical c. So Plato’s first premise is one or more of the following: Knowledge has as its objects: o o o what ise ( = w hat exists). what isp (= what is real[ly F ]. what isv (= what is the case, i.e., is t rue). I t is most plausible to construe these as conditionals: o o o (K e) if K x, then x exists (K p) if K x, then x [ really] is [ F ] (K v) if K q, then q is t rue I n (K e) knowledge = acquaintance: If you know (i.e., are acquainted with) something, t hen that thing exists. I n (K v), we have p ropositional k nowledge: If you know something, then that thing is t rue. ( K p) seems to dissolve into the other two, depending on whether we take knowledge t o be acquaintance or propositional knowledge: o o If you are acquainted with something, then that thing is real (i.e., e xists). If you know, about something, that it is F , then (it is t rue t hat) i t is F . So we can restrict our attention to (K e) and (K v). d. Plato’s second premise (“knowledge is infallible”) seems to make the t ruth of his first p remise a matter of necessity: Necessarily, (K e): What you know m ust exist. Necessarily, (K v): What you know m ust be t rue. A ll of these seem plausible enough; but as we shall see, Plato slides from these i nnocuous sounding premises to rather startling conclusions. E valuation of the a rgument a. Phase One: Are the premises innocuous? That is, can they be accepted by one not antecedently committed to the Theory of Forms? (Remember, Plato is arguing for the existence of Forms from features of the concept of knowledge.) To claim that knowledge is i nfallible seems innocent enough, for all it seems to say is that knowledge entails t ruth: Necessarily, if you know that q, then q is t rue. B ut Plato slides from this innocuous reading of the premise to a more controversial one: that the things that we know are n ecessary t r uths; that what we know is not merely an existent, but something which must exist (a n ecessary being ). I n the case of ‘ise’, the t ransition is from “What is known must exist” to “What is k nown is a necessary existent.” I n the case of ‘isv’, the t ransition is from “What is known must be t rue” to “What is k nown is a necessary t ruth.” B ut this is a now-familiar modal fallacy, conflating the necessity of a conditional s tatement (necessitas consequentiae) with the necessity of the consequent of that s tatement (necessitas consequentis). Necessitas consequentiae necessarily (if p, then q) (p → q) Necessitas consequentis vs if p t hen necessarily . q vs p → q . (p → q) may be t rue even though both p and q a re contingent t ruths. Hence, it does not entail p → q. Example: Necessarily, if Tom’s shir t is crimson, then Tom’s shirt is r ed. (Being crimson entails being red.) But although Tom’s shirt is crimson, i t is not a necessary t ruth that Tom’s shir t is red. The color of Tom’s shirt is a contingent m atter. Cf. Parmenides’ t reatment of the claim “what exists must exist.” T his fallacy vitiates phase one of Plato’s argument: the argument that takes us from t he t ruism that knowledge entails t ruth to the controversial thesis that what is k nown is a necessary t ruth. ...
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