George Berkeley investigates the primary causes of error, skepticism, and difficulty in the sciences, tracing them back to the misconception of abstract general ideas and the false belief in material substance. He demonstrates that the objects of human knowledge are simply ideas actually imprinted on the senses, perceived by attending to the passions and operations of the mind, or formed by memory and imagination.
The central argument rests on the proposition that the existence of unthinking things without any relation to their being perceived is a contradiction. The very being of a sensible thing is to be perceived, meaning physical objects cannot possess an unthinking substance or substratum outside a mind. Berkeley examines primary and secondary qualities, proving that extension, figure, and motion are equally dependent on perception as color, taste, and sound.
From this premise, Berkeley concludes that there is no other substance than spirit, or that which perceives. Because passive and inert ideas cannot produce changes, the continuous succession of ideas and the regular laws of nature must depend upon an incorporeal active substance, or an infinite and wise Spirit who causes them.
Berkeley addresses numerous objections, including the apparent reality of the material world, the distinction between dreams and waking reality, the problem of distance in vision, and the continuity of objects when unobserved by humans. He explains that things continue to exist because they are perceived by other created spirits or, ultimately, by the eternal mind of God.
The work also applies these principles to natural philosophy and mathematics, challenging the infinite divisibility of finite extension and rejecting the search for non-spiritual causes. By eliminating matter and abstraction, Berkeley aims to clear away endless philosophical disputes, silence atheism and skepticism, and direct attention toward God and moral duty.
