self-evident propositions. The line that divides these two ought to be marked as distinctly as possible, and principles that are really self-evident reduced to general axioms. Although first principles do not admit of direct proof, yet there must be certain marks by which those that are truly such may be distinguished from counterfeits. These marks ought to be described and applied to distinguish the genuine from the spurious.… This is a subject of such importance that if inquisitive men can be brought to the same unanimity in the first principles of the other sciences as in those of mathematics and natural philosophy, this might be considered as a third grand era in the progress of human reason.' Thus in 1774 Reid's thought still converges on the subject which had engaged him since the Treatise of Human Nature found its way into the manse of New Machar. Perhaps he was unduly sanguine in expecting unanimity regarding the ingredients of the final reason of mankind—so imperfectly developed in the individual consciousness, in its higher elements, as long as men are disposed to resist the final venture of the heart and conscience in their interpretation of the world and of human life.
It was in 1774 that Reid's appeal in 1764 to the common reason of human nature aroused hostile criticism. He had been seconded by others in his response to the sceptics. The resort to a 'sense' of self-evident truth, in his Inquiry in 1764, which itself looked like a reply to argument by feeling, was followed in 1766 by An Appeal to Common Sense on behalf of Religion, by Dr. James Oswald, minister of Methven in Perthshire. In 1770 Beattie's Essay on the Nature and Immutability of Truth, in opposition to Sophistry and Scepticism, followed. Oswald and Beattie were not
