us into such sentiments as seem to turn into ridicule all our past pains and industry, and to discourage us from all future inquiries. Nothing is more curiously inquired after by the mind of man than the causes of phenomena; nor are we content with knowing the immediate causes, but push on our inquiries till we arrive at the original and ultimate principle. This is our aim in all our studies and reflections. And now we must be disappointed when we learn that this tie lies merely in ourselves, and is nothing but that determination which is acquired by custom. Such a discovery not only cuts off all hope of ever attaining satisfaction, but even prevents our very wishes; since it appears that when we desire to know the ultimate and operating principle or something which resides in the external object, we only contradict ourselves, or talk without a meaning.… The intense view of these manifold contradictions and imperfections in human reason has so wrought upon me and heated my brain, that I am ready to reject all belief and reasoning, and can look at no opinion even as more probable or likely than another. All who believe anything, on any subject, with certainty, must be fools.’
This is the issue of the Treatise of Human Nature when the logical understanding is finally resolved into transitory and isolated feelings, without permitted final postulates of reason, in the form of faith or in any other form, to connect and interpret them.
It was this issue that Reid took seriously. He set himself, at first for his own satisfaction only, to consider the ground he had for trusting experience, when Hume reported that experience dissolved into sensational atoms. Accordingly he spent much of his time at New Machar in reflecting first of all on his perceptions through the senses. He began with these, because it seemed that even as the foundations of abstract mathematics lie in the mathematical axioms and definitions, so the foundations of all concrete reasoning are to be found in the rational constitution of perception through the five senses. 'In the tree
