Measured by the present standard of Aristotelian criticism, Reid’s exposition of the Organon, and estimate of its place in the development of human understanding, may seem meagre and inadequate; especially as the issue of seven years of preparation, and as his solitary contribution to philosophy in these sixteen years. But when we remember that Aristotelian logic was then under an eclipse, especially in Scotland, and that Reid’s ‘Brief Account’ was an attempt to draw the Organon out of the obscurity to which it had been condemned by leaders of modern thought, the merit of his sober and sagacious commentary may be more recognised. It is as a signal monument of abstracted intellectual activity, rather than as a philosophical instrument for advancing or organising our knowledge, that Reid regards the syllogistic logic. He concludes that the art of syllogism is better fitted to promote scholastic litigation than real improvement in the sciences; he sees in it only ‘a venerable piece of antiquity and a great effort of human genius.’ When he contrasts the utility of Bacon’s _Organum_, as a factor in the progressive intelligence of mankind, he fails to see that each Organon may consistently supplement the other. Reid characteristically ends his account of the old Organon by suggesting an Organon, different from either the old or the new, as still wanting. This should neither, like Aristotle’s, unfold only abstract forms of deductive reasoning, nor, like Bacon’s, only methods for verifying inductive generalisations. It should be concerned with the rational principles which compose the Common Sense of mankind. ‘All the real knowledge of mankind may be divided into two parts: the first consists of self-evident propositions, the second of those which are deduced by just reasoning from 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