Now the popular logic of the day,--the logic which has long been taught in our schools and universities--has three sources.--In the first place, but in a slight degree, it trenches upon the province of psychology, and gives some account of the operation by which concepts or general ideas are supposed to be formed, and of the errors or fallacies which naturally creep into the process of reasoning. This is the more strictly modern, the descriptive part of our logic-books.--But, secondly, the logic of our youth rests in a much higher degree upon the venerable authority of Aristotle. That logic, within its own compass, was a masterpiece of analysis, and for many centuries maintained an ascendency over the minds of men, which it well deserved. But it was not an analysis of thought or knowledge as a whole, and it treated its subject in fragments. It gave in one place an analysis of science and in another an analysis of certain methods, which could be observed in popular discussions and practical oratory. As Lord Bacon remarked, it did little else than state and, it may be, exaggerate the _rationale_ of argumentation. A high level of popular thought it unquestionably was, which Aristotle had to investigate,--a level which many generations of less favoured races were unable to reach. But there were defects in this Logic which fatally marred its general usefulness, when the limited scope of its original intention had been lost sight of. The thoughts of Greece, it has been said, were greatest and most active in the line of popular action for the city and the public interest, in the discussions, the quibbles, the fallacies, and rhetorical arts of the barber's shop and the 'agora.' The aim of such exercises was to convince, to demonstrate, to persuade, to overcome;--it might be for good and truth, but also it might not. And accordingly the Logic of Aristotle has been said to have for its end and canon the power to convince and to give demonstrative certainty. There is some ground, it may be, for this charge. The ancient logician seems to luxuriate in a rank growth of forms of sophism, and in an almost childlike fondness for variety of argumentative method. He seems resolved to trace the wayward tricks of thought and its phases through every nook and cranny, to exhaust all the permutations and complications of its elements. But let us be just, and remember that all this was in the main a speculative inquiry--for the sake of theory. It developed the powers of judgment and inference, just as the modern research for new metals, new plants, or new planets, develops the powers of observation. Both have some value in the material results they discover: but, after all, the mental culture they give is the main thing. And the talents quickened by deductive research are no whit less valuable than those owed to the other. Forms are essential, even if it be possible to make the terrible mistake of regarding them as all-important to the exclusion of matter.