Dr WHEWELL, ON PLATO'S NOTION OF DIALECTIC. 595 



it ? But on the other hand, if this dichotomous division be a different process from the division 

 called Dialectic in the Phsedrus, had Plato two methods of division of a subject ? and yet has he 

 never spoken of them as two, or marked their distinction ? 



This difficulty would be removed if we were to adopt the opinion, to which others, on other 

 grounds, have been led that the Sophistes, though of Plato's time, is not Plato's work. The 

 grounds of this opinion are, — that the doctrines of the Sophistes are not Platonic : (the doctrine 

 of Ideas is strongly impugned and weakly defended :) Socrates is not the principal speaker, but 

 an Eleatic stranger : and there is, in the Dialogue, none of the dramatic character which we 

 generally have in Plato. The Dialogue seems to be the work of some Eleatic opponent of 

 Plato, rather than his. 



(Hep. B. vii.) But we can have no doubt that the Phsedrus contains Plato's real view 

 of the nature of Dialectic, as to its form ; let us see how this agrees with the view of 

 Dialectic, as to its matter and object, given in the seventh Book of the Bepublic. 



According to Plato, Beal Existences are the objects of the exact sciences (as number and 

 figure, of Arithmetic and Geometry). The things which are the objects of sense are 

 transitory phenomena, which have no reality, because no permanence. Dialectic deals with 

 Realities in a more general manner. This doctrine is everywhere inculcated by Plato, 

 and particularly in this part of the Republic. He does not tell us how we are to obtain a 

 view of the higher realities, which are the objects of Dialectic : only he here assumes that 

 it will result from the education which he enjoins. He says (§ 13) that the Dialectic 

 Process (>J $ia\e/cTi/oj ne6o$os) alone leads to true science : it makes no assumptions, but goes 

 to First Principles, that its doctrines may be firmly grounded : and thus it purges the eye of 

 the soul, which was immersed in barbaric mud, and turns it upward; using for this purpose the 

 aid of the sciences which have been mentioned. But when Glaucon inquires about the details 

 of this Dialectic, Socrates says he will not then answer the inquiry. We may venture to say, 

 that it does not appear that he had any answer ready. 



Let us consider for a moment what is said about a philosophy rendering a reason for the 

 First Principles of each Science, which the Science itself cannot do. That there is room for 

 such a branch of philosophy in some sciences, we easily see. Geometry, for instance, proceeds 

 from Axioms, Definitions and Postulates; but by the very nature of these terms, does not 

 prove these First Principles. These — the Axioms, Definitions and Postulates, — are, I conceive, 

 what Plato here calls the Hypotheses upon which Geometry proceeds, and for which it is not 

 the business of Geometry to render a reason. According to him, it is the business of - ' Dialectic'' 

 to give a just account of these " Hypotheses." What then is Dialectic? 



(Aristotle.) It is, I think, well worthy of remark, that Aristotle, giving an account in 

 many respects different from that of Plato, of the nature of Dialectic, is still led in the same 

 manner to consider Dialectic as the branch of philosophy which renders a reason for First 

 Principles. In the Topics, we have a distinction drawn between reasoning demonstrative, and 

 reasoning dialectical: and the distinction is this: — (Top. i. 1) that Demonstration is by 

 syllogisms from true first principles, or from true deductions from such principles : and that the 

 Dialectical Syllogism is that which syllogizes from probable propositions (e£ ivSo^wv). And he 

 adds that probable propositions are those which are accepted by all, or by the greatest part, or by 



