COMMON BASIS OF EMPIRICISM AND RATIONALISM 21 



is a principle which in the history of philosophy may be said to 

 date from Empedocles of Acragas, but which common sense has 

 no doubt held from time immemorial. Not that either philos- 

 ophy or common sense has always been agreed upon the matter. 

 Indeed, as a philosophical dogma, nobody would ever have 

 thought of asserting such a proposition, had it not previously been 

 denied. With Empedocles it was simply a reassertion of the 

 trustworthiness of clear perception which in the previous period of 

 Greek philosophy had become more and more deeply suspected. 

 The physical theories of the early cosmologists had been so 

 utterly out of accord with ordinary observation that they (or their 

 followers) had inevitably been led to exalt the authority of dis- 

 cursive reason as over against that of direct observation; until 

 with Heraclitus, and still more with Parmenides, an absolute 

 scepticism of the senses resulted. 



In the generation following Empodocles this scepticism took 

 on a new and more subtle form. According to a theory ascribed 

 to Protagoras, the senses are indeed absolutely trustworthy in 

 so far as they simply make each man aware of his own perceptive 

 states of consciousness; but they give him no insight into the 

 sensations of other men or into the nature of things. The notion 

 of an indubitable immediate experience is thus preserved; but 

 the range of its significance is seriously restricted. This doctrine 

 of the relativity of sense-perception was maintained by all of the 

 more important thinkers of antiquity (except the Stoics) ; and 

 in modern times it has been held by both rationalists and em- 

 piricists. Certain of the latter, indeed, have made it a ground 

 for doubting, or denying altogether, the existence of any object 

 over and above the sensations themselves. 



A second form of immediatism philosophy owes to Plato. 

 Desiring, as a constructive social reformer, to found the theory 

 and practice of politics upon a basis of indubitable truth, it 

 appeared clear to him that Protagoras had taken away the hope 

 of discovering such a basis in the evidence of the senses. Yet he 

 saw that as a matter of our life-history all knowledge starts from 



