[106] Lord Macaulay has some pertinent and characteristic remarks concerning this topic in his literary estimate of Dr. Johnson. "How it chanced that a man who reasoned on his premises so ably, should assume his premises so foolishly, is one of the great mysteries of human nature. The same inconsistency may be observed in the schoolmen of the middle ages. Those writers show so much acuteness and force of mind in arguing on their wretched data, that a modern reader is perpetually at a loss to comprehend how such minds came by such data. Not a flaw in the superstructure of the theory which they are rearing escapes their vigilance. Yet they are blind to the obvious unsoundness of the foundation. It is the same with some eminent lawyers. Their legal arguments are intellectual prodigies, abounding with the happiest analogies and the most refined distinctions. The principles of their arbitrary science being once admitted, the statute-book and the reports being once assumed as the foundations of reasoning, these men must be allowed to be perfect masters of logic. But if a question arises as to the postulates on which their whole system rests, if they are called upon to vindicate the fundamental maxims of that system which they have passed their lives in studying, these very men often talk the language of savages or of children." (_Essays_, Ed. 1852. p. 175.) As to the schoolmen, any one who wishes to form a fair idea of their acuteness with little trouble to himself, may consult the "Synopsis Distinctionum" of H. L. Castanæus, a book found in most learned libraries. [y] See Additional Note E.--The great interest of this subject for our purpose lies in the circumstance that the relation of Theory to Fact is in effect a question most closely akin to the one already mooted concerning the relation of our Sensations to our Perceptions (compare Additional Note B). These two questions are indeed so very similar as to be in the main identical. What we want to learn regarding both relations, is, _first_, the _extent_ of the relativity to our human nature; in other words how _much we_ have _mentally put_ into our Theories and Sensations _before_ we treat them as Facts and Perceptions. _Secondly_, what reason we have for believing _any_ of our knowledge comprehended under either or both of these relativities (Perception and Fact) to be true _beyond_ our human sphere; and, above all, whether we are able to assert, on good grounds, that such and such parts of either kind of our knowledge are absolutely and immutably true?--