The child which overbalances itself in learning to walk is experimenting on the law of gravity.

I am convinced that it is impossible to expound the methods of induction in a sound manner, without resting them upon the theory of probability. Perfect knowledge alone can give certainty, and in nature perfect knowledge would be infinite knowledge, which is clearly beyond our capacities. We have, therefore, to content ourselves with partial knowledge - knowledge mingled with ignorance, producing doubt.

It is clear that Economics, if it is to be a science at all, must be a mathematical science ... simply because it deals with quantities... As the complete theory of almost every other science involves the use of calculus, so we cannot have a true theory of Economics without its aid.

Value is the most invincible and impalpable of ghosts, and comes and goes unthought of, while the visible and dense matter remains as it was.

Repeated reflection and inquiry have led me to the somewhat novel opinion, that value depends entirely upon utility.

Science arises from the discovery of Identity amid Diversity.

The whole value of science consists in the power which it confers upon us of applying to one object the knowledge acquired from like objects; and it is only so far, therefore, as we can discover and register resemblances that we can turn our observations to account.