270 ELEMENTS OF SCIENCE 



universally they may exist amongst our fellow men. If 

 only we know that we ourselves are conscious and can 

 reflect, mentally abstract, and judge, and know that we 

 are so doing, that is enough to make us absolutely certain 

 we possess a power, different indeed from each and all the 

 powers which have been previously spoken of in this 

 little work. Moreover, this knowledge is the most 

 absolutely certain of all knowledge. However we may 

 doubt, we cannot doubt that we think while we are 

 thinking, whatever may be the object of our thoughts. 

 And thought is our ultimate test of truth. Even in 

 investigating the properties of material bodies, it is to 

 thought we must ultimately appeal. Only by that can 

 we know what we may have done, and it is that which 

 judges between conflicting indications of different sense- 

 impressions. Our senses are truly tests of certainty, but 

 not the test. Self-conscious, reflective thought is and 

 must be our last and ultimate criterion. 



And now let the reader consider what his own intel- 

 lect tells him about its own powers and activities as 

 revealed to him directly in his consciousness. He will 

 recognise that his intellect (that is, he himself) exists 

 continuously, so that he knows that it is that same in- 

 tellect of his which both began to think of this question, 

 and now still continues to think about it. He will 

 also recognise that he knows objects and persons about 

 him, and what is happening to them before his eyes, while 

 he all the time remains something distinct from them. 

 He can reflect over the different things he remembers to 

 have thought of during the morning, and recognise that 

 they have constituted a series of thoughts. He can thus 

 think of them as a whole a series or he can select one 

 of his thoughts, or a group of them, for reconsideration. 

 He knows also what he is about, what he is doing, or 



