results: out of a list of thirty-one, seven certainly wrote memoirs or other works under twenty; fifteen gave out their first known production between twenty and twenty-five; three began to write between twenty-five and thirty; leaving six who, so far as I can judge, entered on the productive stage after thirty.
If, again, we ask at what age fame, or the achievement which entitles to fame, is reached, we obtain the following figures: Out of a group of thirty-seven, fourteen reached this point before twenty-five, twelve between twenty-five and thirty; eight between thirty and forty; while three did not rise to the height of renown till after forty.
In science, as in the more serious department of letters, fame is sometimes reached suddenly by the production of a great work, the fruit of many years of study. Harvey's publication of his great discovery at the age of fifty is a case in point. It is to be remembered, however, that Harvey had expounded his theory in lectures some twelve years before this date. And the same kind of remark applies to Darwin and others who first gave to the world epoch-making truths at a somewhat advanced age; we commonly find that the actual discovery dates from a much earlier period, the promulgation of it being deferred till it was ready to be presented in a definite and verified form. The case of Franklin making his first, and this a capital, scientific discovery toward the age of fifty is, so far as I can gather?, exceedingly rare, if not, strictly speaking, unique.
Philosophers.—If philosophy precedes science in the historical development of the race, we need not wonder at meeting with instances of youthful speculative genius. Coleridge is not the only case of a lad of fifteen having his head seething with metaphysical puzzles. But Coleridge, it may be said, never developed into an original thinker; and what we require is proof of the early manifestation of genuine philosophic originality.
Passing by the romantic story of Abélard dazzling Paris and Europe with his dialectics at the age of twenty, and coming to the modern period, we note that the most conspicuous instances of philosophical precocity are supplied by the history of British philosophy. Berkeley, as his commonplace-book shows, hit on his new principle of idealism at college when only eighteen, an instance of metaphysical audacity to which there is no parallel. His "New Theory of Vision," perhaps the most epoch-making work in the history of psychology, appeared when the author was twenty-four. His immediate successor, Hume, displayed speculative ability when very young, and was regarded by his mother as an "uncommon wake-minded" lad. His "Treatise of Human Nature," probably the work of modern times which has proved most stimulating to further inquiry, was thought out between the ages of twenty-three and twenty-six. And, oddly enough, Hume's most distinguished follower, J. S. Mill, has supplied the best recent example of philosophic precocity.
