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52 CHAPTER VII GRATRY ON LOGIC

Logic used to beexpressed in Geometric or quasi-Geometric diagrams. We now write it usually in a terminology borrowed from Algebra.

Modern Mathematical Logic may be said to be a tree, whose root is represented by the Newtonian Fluxion-method; and its trunk by the Logique of Gratry ; while its main branches are such works as those of Babbage, De Morgan, Boole, and Hinton; and the Sciences of Quaternions and of the so-called Fourth-Dimensional Mathematics. Carrying on the same simile, we might add that the numerous little twigs of special methods thrown off from the main boughs would have all the more chance of being fruitful if they were not so ready to sever their connection with the stock from which they sprang. As a matter of chronology, the treatises of Babbage, De Morgan, and Boole were published before the first appearance of the Logique. But then it must be remembered that Science is not created by the printer; books merely represent, in visible form, a thought-growth which has its actual existence in the Mind of Humanity ; and the chronological order in which the several parts of a new Science are projected on to the surface of Literature is not always identical with the order in which they were evolved. Mathematical Logic will be best understood by those who