Locke then proceeds to show in detail how certain complex ideas are formed out of simple ones. The idea of space is got by the senses of sight and touch together; certain combinations of relations in space are measures, and the power of adding measure to measure without limits is that which gives the idea of immensity.
Figure is the relation which the parts of the termination of a cir cumscribed space have within themselves. He then proceeds to refuto the Cartesian doctrine, that body and extension are the same ; and maintains that while body is full space is empty, and that all bodies may easily pass into it ; and while the latter is not physically divisible, that Is, has not moveable parts, the parts of the former arc moveable, and itself is physically divisible. What however space is actually, is left undetermined. He asserts the existence of a vacuum beyond the utmost bounds of body, and this is proved by tho power of annihilation and the possibility of motion. The idea of succession arises from the perception of a continued series of sensations, and by observing the distance between two parts of the series we gain the idea of duration, which, when determined by a certain measure, suggests that of time; and as wo arrive at the idea of immensity by the perception that we can enlarge any given extension without limit, so the unchecked repetition of succession originates that of eternity. That of power is formed partly by a perception that outward objects are produced and destroyed by others, partly by that of the action of objects on the senses, but chiefly from that of the mind's internal operations. The latter suggests the idea of active power, the former of passive. Now the will is the power of producing the presence or absence of a parti cular idea, or to produce motion or rest, and liberty is the power to think or not, to act or not to act, according as appears good to the mind. The will is determined by the understanding, which itself is influenced by a feeling of the unfitness of a present etato, which is called desire.
As to the origin of the idea of substance :—we often find certain ideas connected together ; and in consequence of this invariable aseo elation, we conceive of them as a single idea ; and as the qualities which originate these ideas have no separate subsistence in themselves, we are driven to suppose the existence of a 'somewhat' as a support of these qualities. To this somewhat we give the name of substance,
and relatively to it all qualities are called accidents.
Of the ideas of relation, those of cause and effect are got from the observation that several particulars, both qualities and substances, begin to exist, and receive their existence, from the due application and operation of some,other being. In the same manner the ideas of identity and diversity are derived from experience. When we compare an object with itself at different times and places, and find it to be the same, we arrive at the idea of identity. Whatever has the same beginning in reference to time and place is the same, and a material aggregate which neither decreases nor lessens is the same; but in organical and living creatures, identity is determined not merely by the duration of the material mass, but by that of the organical struc ture and the continuance of consciousness. Lastly, moral good and evil are relations. Good and evil are nothing but that which occasions pleasure and pain; and moral good and evil are the conformity of human actions to some law whereby physical good or evil is produced by the will and power of the law-maker. Law is of three kinds : divine law, which measures siu and duty; civil, which determines crime and innocence ; and philosophical, or the law of opinion or reputation, which measures virtue and vice.
Having thus examined the origin and composition of ideas, Locko proceeds to determine their general characters. He divides them accordingly into clear and obscure, distinct and confused, into real and fantastical, adequate and inadequate, and, lastly, into true and false. In treating of this last distinction, he observes that all ideas are in themselves true; and they are not capable of being false until some judgment is passed upon them, or, in other words, until something is asserted or denied of them. But there is also this property in ideas, that one suggests another, and this is the so-called association of ideas.