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Ladies and Gentlemen:
For eight abbreviated hours I am to endeavor to occupy your attention with the subject of reasoning. But can one person inform another what is good reasoning and what is bad?
About seventy generations have passed since Aristotle gave to logic a scientific form. There has not been one of those generations in Europe that has not been occupied with this study and it is natural and proper to ask what the harvest has been. At the end of sixty of those seventy generations, Europeans reasoned no better than the personages of Plato's Dialogues are represented as reasoning. They were more considerably more adroit,— they reached their conclusions with greater facility; but the conclusions
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were neither more sure nor further-reaching; and as to the character of the reasoning, it was of a decidedly less vigorous and fecund kind than that of Plato himself. As for the science of logic, if remained substantially the very doctrine that Aristotle had taught.
Galileo inaugurated the science of dynamics about 1590, and his work was well-known and had its effect, although his book was not published for near half a century later; and it was the study of dynamics, more than anything else, which gradually taught men to reason better on all subjects. I do not say that it was the sole cause; for Tycho Brahe established his observatory half a dozen years before Galileo was appointed professor in Pisa; and the principle of our system of
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Ladies and Gentlemen:
The most prominent peculiarity of the system of logic which my studies have led me to adopt is that instead of being satisfied with the almost universal division of all reasoing into Necessary and Probable Reasoning, I find myself forced to recognize three grand branches, Deduction Induction Abduction.
Because this doctrine is almost peculiar to myself as yet, having only been preached by one obscure pen for only thirty or forty years, which is a short time in the development of such broad
