XXV. On Plato's Notion of Dialectic. By W. Whewell, D.D. Master of 



Trinity College. 



[Read May 7, 1855.] 



The survey of the sciences, arithmetic, plane geometry, solid geometry, astronomy and 

 harmonics — which is contained in the seventh Book of the Republic (§ 6 — 12), and which has 

 been discussed in the preceding paper, represents them as instruments in an education, of 

 which the end is something much higher — as steps in a progression which is to go further. 

 "Do you not know," says Socrates, (^ 12) "that all this is merely a prelude to the strain 

 which we have to learn ?* And what that strain is, he forthwith proceeds to indicate. 

 " That these sciences do not suffice, you must be aware : for — those who are masters of such 

 sciences — do they seem to you to be good in dialectic ? (Setvol SiaXeKTiKol elfai ;) 



" In truth, says Glaucon, they are not, with very few exceptions, so far as I have fallen 

 in with them." 



"And yet, said I, if persons cannot give and receive a reason, they cannot attain that 

 knowledge which, as we have said, men ought to have." 



Here it is evident that " to give and to receive a reason," is a phrase employed as 

 coinciding, in a general way at least, with being "good in dialectic;" and accordingly, this is 

 soon after asserted in another form, the verb being now used instead of the adjective. " It is 

 dialectic discussion (to <tia\e<ye<r9ai,) which executes the strain which we have been preparing". 

 It is further said that it is a progress to clear intellectual light, which corresponds to the progress 

 of bodily vision in proceeding from the darkened cave described in the beginning of the Book 

 to the light of day. This progress, it is added, of course you call Dialectic (<iia\eKTiKijv). 



Plato further says, that other sciences cannot properly be called sciences. They begin 

 from certain assumptions, and give us only the consequences which follow from reasoning on 

 such assumptions. But these assumptions they cannot prove. To do so is not in the province 

 of each science. It belongs to a higher science : to the science of Real Existences. You call 

 the man Dialectical, who requires a reason of the essence of each thing*. 



And as Dialectic gives an account of other real existences, so does it of that most important 

 reality, the true guide of Life and of Philosophy, the Real Good. He who cannot follow this 

 through all the windings of the battle of Life, knows nothing to any purpose. And thus 

 Dialectic is the pinnacle, the top stone of the edifice of the sciences'!". 



Dialectic is here defined or described by Plato according to the subject which it treats, and 

 the object with which it is to be pursued : but in other parts of the Platonic Dialogues, 



* T H Kai StaXeicriKdv KaXeTs tov \6yov eKaa-rov XafifSdvovra Ttjt ouo-ias ; (§ 14) 

 ■f- aiwrep dpiyydv toIs fiaBriuaatv tj SiaXeicriKi) rjfiiv eirdvai Keltrdai. (§ 14) 



