Cause And Effect

In the notice that our senses take on the constant vicissitude of things, we cannot but observe that several particular, both qualities and substances, begin to exist, and that they receive this their existence from the due application and operation of some other being.  From this observation we get our ideas of cause and effect.  That which produces any simple or complex idea we denote by the general name, cause, and that which is produced, effect.  Thus finding that in that substance which we call wax, fluidity, which is a simple idea that was not in it before, is constantly produced by the application of a certain degree of heat; we call the simple idea of heat, in relation to fluidity in wax, the cause of it, and fluidity the effect.

-- John Locke (1632 - 1704), English philosopher and social contract theorist, An Essay Concerning Human Understanding (1689), Of Cause And Effect, And Other Relations