This program examines the philosophies of British empiricists John Locke and George Berkeley. Philosopher Michael Ayers of Oxford interprets Locke's skeptical theory that all knowledge is sensory and speculative, and that the true nature of the world can never be known as an attack on Descartes' theory of innate ideas. Conversely, Berkeley insists that we cannot have sensory knowledge of material substances because the exist only in the mind. Even the laws of nature, Berkeley says are merely the regularities of our own perceptions or ideas.