Hume’s philosophy being the suicide of intelligence, can hardly be spoken of as a 'system.' It is not constructive, but wholly destructive, and therefore a negation of system, philosophic or other, in a finally speechless and motionless agnostic doubt.
Hume’s letter to Reid was his only rejoinder to the Inquiry. In 1763 he had ceased to produce philosophical books. His recognition of the 'deeply philosophical' nature of Reid’s argument is a testimony to the worth of the work on which Reid's literary reputation chiefly rests. The 'share of the praise' which Hume claims, Reid was ready to concede. 'I hope,' he says in the Dedication of the Inquiry, 'I hope that the author of this sceptical system wrote it in the belief that it would be useful to mankind. And perhaps it may prove so at last. For I conceive the sceptical writers to be a set of men whose business it is to pick holes in the fabric of knowledge wherever it is weak and faulty; and when those places are properly repaired, the whole building becomes more firm and solid than it was formerly.' And, in fact, the intellectual progress of mankind has been sustained by an alternation of sceptical and conservative philosophies.
After prolonged cogitation, the 'weak and faulty' place in the 'fabric' of modern philosophy seemed to Reid to lie in an unproved assumption with which modern philosophers set out in their speculations. For they took for granted that only the sensations and ideas within each mind could be perceived: yet we naturally 'believe that we are seeing and handling the very outward things themselves' that make what is called the material world. If the philosophers are right, we have no immediate revelation of the qualities of outward things, and no evidence of their
