The “materialistic” hypothesis—­so Berkeley terms the assumption that a material world exists apart from perceiving mind, and independently of being perceived—­is, first, unnecessary, for the facts which it is to explain can be explained as well, or even better, without it; and, second, false, since it is a contradiction to suppose that an object can exist unperceived, and that a sensation or idea is the copy of anything itself not a sensation or idea.  Ideas are the only objects of the understanding.  Sensible qualities (white, sweet) are subjective states of the soul; sense objects (sugar), sensation-complexes.  If sensations need a substantial support, this is the soul which perceives them, not an external thing which can neither perceive nor be perceived.  Single ideas, and those combined into objects, can exist nowhere else than in the mind; the being of sense objects consists in their being perceived (esse est percipi).  I see light and feel heat, and combine these sensations of sight and touch into the substance fire, because I know from experience that they constantly accompany and suggest each other.[1] The assumption of an “object” apart from the idea is as useless as its existence would be.  Why should God create a world of real things without the mind, when these can neither enter into the mind, nor (because unperceived) be copied by its ideas, nor (because they themselves lack perception and power) produce ideas in it?  Ideas signify nothing but themselves, i. e., affections of the subject.

[Footnote 1:  The fire that I see is not the cause of the pain which I experience in approaching it, but the visual image of the flame is only a sign which warns me not to go too near.  If I look through a microscope I see a different object from the one perceived with the naked eye.  Two persons never see the same object, they merely have like sensations.]

The further question arises, What is the origin of ideas?  Men have been led into this erroneous belief in the reality of the material world by the fact that certain ideas are not subject to our will, while others are.  Sensations are distinguished from the ideas of imagination, which we can excite and alter at pleasure, by their greater strength, liveliness, and distinctness, by their steadiness, regular order, and coherence, and by the fact that they arise without our aid and whether we will or no.  Unless these ideas are self-originated they must have an external cause.  This, however, can be nothing else than a willing, thinking Being; for without will it could not be active and act upon me, and without ideas of its own it could not communicate ideas to me.  Because of the manifoldness and regularity of our sensations the Being which produces them must, further, possess infinite power and intelligence.  The ideas of imagination are produced by ourselves, real perceptions are produced by God.  The connected whole of divinely produced ideas we call nature, and the constant regularity in their succession, the laws of nature.  The invariableness of the divine working and the purposive harmony of creation reveal the wisdom and goodness of the Almighty more clearly than “astonishing and exceptional events.”  When we hear a man speak we reason from this activity to his existence.  How much less are we entitled to doubt the existence of God, who speaks to us in the thousandfold works of nature.