*THE POPULAR SCIENCE MONTHLY.*

culus of reasoning had, at different times, occupied Boole's thoughts, but it was not till the spring of 1847 that a memorable logical controversy led him to put his ideas into a definite form. He afterward regarded this pamphlet as a hasty and imperfect exposition of his logical system, and desired that his much larger work, "An Investigation of the Laws of Thought," etc. (1854), should alone be considered as containing a mature statement of his views.

This is Boole's greatest work, and is an attempt to apply the symbols and operations of mathematics to logic and the laws of thinking. The object of the work, as stated by himself, is "to investigate the fundamental laws of those operations of the mind by which reasoning is performed; to give expression to them in the symbolical language of a calculus, and upon this foundation to establish the science of logic and construct its method; to make that method itself the basis' of a general method for the application of the mathematical doctrine of probabilities; and, finally, to collect from the various elements of truth, brought to view in the course of these inquiries, some probable intimations concerning the nature and constitution of the human mind."

Of this work Professor Todhunter, in the preface to his "History of the Theory of Probabilities," speaks as "marvelous"; and, in similar language, Professor W. Stanley Jevons speaks of it as "one of the most marvelous and admirable pieces of reasoning ever put together."

It is often supposed that mathematicians are deficient in judgment and knowledge of other matters. In Boole this was not the case; for, though he published little except his mathematical and logical works, his acquaintance with general literature was wide and deep. Dante was his favorite poet, and he preferred the "Paradiso" to the "Inferno." The metaphysics of Aristotle, the ethics of Spinoza, the philosophical works of Cicero, and works of a kindred character, were frequent subjects of his study.

The personal character of Boole inspired all his friends with the deepest esteem. He was marked by the modesty of true genius, and his life was given to the single-minded pursuit of truth. Though he received a royal medal for his memoir ("Philosophical Transactions of the Royal Society," 1844), and the honorary degree of LL. D. from the University of Dublin, it may be said that he neither sought nor received the ordinary rewards to which his discoveries entitled him.

"On the 8th of December, 1864, in the full vigor of his intellectual powers," says W. Stanley Jevons, in his tribute to his friend's life and genius, "George Boole died of an attack of fever, ending in suffusion on the lungs."

The mathematical and logical works of Boole are by far too abstruse to admit of their being used as text-books in schools of even the highest grades; but as works of reference they are invaluable to advanced students and the special cultivators of pure mathematics and the profounder problems of logic.