SIR WILLIAM Hamilton's philosophy. 223 



pies is such as must have led him to deny that necessity is their 

 differentiating attribute. A brief glance at this doctrine may not be 

 useless in enabling us more correctly to interpret the philosophy of 

 Eeid. 



According to this doctrine,"!" fi^'^^ principles are those which all 

 reasoning in the last appeal implies, inasmuch as the inference of one 

 truth from another cannot have proceeded without a beginning, but 

 must have started from some truth or truths which are not themselves 

 inferred from any prior truth. Such truths, as being prior to all 

 others in human knowledge, are cslledi first principles; and since they 

 do not draw their evidence from others, must contain it in themselves. 

 Self-evidence is therefore the distinctive characteristic of first prin- 

 ciples. There is, however, a difference of opinion among men, as to 

 what truths are self-evident, and accordingly it is necessary to inquire 

 whether there is "no mark or criterion by which first principles that 

 are truly such may be distinguished from those that assume the 

 character without a just title." In answering the question which he 

 thus proposes, we should certainly expect to find what Reid considered 

 to be the criterion of first principles ; and yet, in the four propositions 

 with their corollaries which form his answer, while there is an enume-' 

 ration of several tests, some of which are most inapplicable, there is 

 no mention of the criterion which is now recognized. The only pas-- 

 sages in which this criterion is explicitly referred to, as far as I can 

 recollect and as far as Sir William Hamilton quotes, are at pp. 455, 

 459 and 521 in his edition of Reid's works, where, among other evi- 

 dences, necessity is adduced as proving the non-empirical character of 

 the two principles, that every beginning of existence must have a 

 cause, and that intelligence in the cause may be inferred from the 

 marks of it in the effect. In these passages undoubtedly Reid sees 

 that a proposition, which we know to be true necessarily, and there- 

 fore true in all places and at all times, cannot be obtained by an in- 

 duction, however extensive, of our experiences ; but waiving the con- 

 sideration that he here mis-states a subjective necessity of knowledge 

 as the knowledge of an objective necessity, we must notice, what does 

 not seem to be observed by Hamilton, that Reid's classification of first 

 principles is sufficient to shew that he would have refused to constitute 

 necessity the criterion of them all. For he divides truths into the 

 two classes of contingent and necessary, while he allocates to each of 



^Intellectual Powers, Essay VI., Chapters 4-7. 

 Vol. XI. Q 



