Have we not hereditary possessions in our just laws, our free and nobly developed constitution, our rich literature and philosophy, incomparably abov… - William Stanley Jevons

One of the first and most difficult steps in a science is to conceive clearly the nature of the magnitudes about which we are arguing.

By a commodity we shall understand any object, substance, action or service, which can afford pleasure or ward off pain.

By induction we gain no certain knowledge; but by observation, and the inverse use of deductive reasoning, we estimate the probability that an event which has occurred was preceded by conditions of specified character, or that such conditions will be followed by the event. ...I have no objection to use the words cause and causation, provided they are never allowed to lead us to imagine that our knowledge of nature can attain to certainty. ...We can never recur too often to the truth that our knowledge of the laws and future events of the external world are only probable.