It is perfectly true that the discovery of each new portion of knowledge enables men to acquire it who might never have acquired it otherwise; but as the acquisition of the details of knowledge becomes facilitated, the number of details to be acquired increases at the same time; and the increased ease of acquiring each is accompanied by an increased difficulty in assimilating even those which are connected most closely with each other.

We may safely say that a knowledge of the simple rules of arithmetic is common to all the members of the English University of Cambridge; but out of some thousands of students only a few become great mathematicians.

And the same thing holds good of scientific knowledge in general, and especially of such knowledge as applied to the purposes of practical industry.

Knowledge and inventions, once made, are like a river which flows by everybody; but the water of the river becomes the property of individuals only in proportion to the quantity of it which their brains can, as it were, dip up; and the knowledge dipped up by the small brains is no more equal to that dipped up by the large than a tumbler of water is made equal to a hogshead by the fact that both vessels have been filled from the same stream.
Let us now pass on to the argument which, differing essentially from the preceding in that it does not aim at proving that the great men are commoner than they seem to be, or their knowledge more diffused, insists that of what the great men seem to do very little is really their own--or that, as Mr.Bellamy puts it, in words which we have already quoted, "nine hundred and ninety-nine parts out of a thousand of their produce is really the result of their social inheritance and environment." Here, again, we have a statement, which from one point of view is true.

It is merely a specialised expression of the far more general doctrine that the whole process of the universe, man included, is one, and that all individual causes are only partial and proximate.
No man at any period could do the precise things that he does if the country in which he lives had had a different past or present, any more than he could do anything if it were not for his own previous life, for the fact that he had been born, that his mind and body had matured, and that he had acquired, as he went along, such and such knowledge and experience.