I mean by Science the application of experience to new circumstances, by the aid of an order of nature which has been observed in the past, and on the assumption that such order will continue in the future. The simplest use of experience as a guide to action is probably not even conscious; it is the association by continually-repeated selection of certain actions with certain circumstances, as in the unconsciously-acquired craft of the maker of flint implements. I still call this science, although it is only a beginning; because the physiological process is a type of what takes place in all later stages. The next step may be expressed in the form of a hypothetical maxim,--'If you want to make brass, melt your copper along with this blue stone.' To a maxim of this sort it may always be replied, 'I do not want to make brass, and so I shall not do as you tell me.' This reply is anticipated in the final form of science, when it is expressed as a statement or proposition: brass is an alloy of copper and zinc, and calamine is zinc carbonate. Belief in a general statement is an artifice of our mental constitution, whereby infinitely various sensations and groups of sensations are brought into connection with infinitely various actions and groups of actions. On the phenomenal side there corresponds a certain cerebral structure by which various combinations of disturbances in the sensor tract are made to lead to the appropriate combinations of disturbances in the motor tract. The important point is that science, though apparently transformed into pure knowledge, has yet never lost its character of being a craft; and that it is not the knowledge itself which can rightly be called science, but a special way of getting and of using knowledge. Namely, science is the getting of knowledge from experience on the assumption of uniformity in nature, and the use of such knowledge to guide the actions of men. And the most abstract statements or propositions in science are to be regarded as bundles of hypothetical maxims packed into a portable shape and size. Every scientific fact is a shorthand expression for a vast number of practical directions: if you want so-and-so, do so-and-so.