Difficult Books

In The Life of Samuel Johnson, James Boswell recalls speaking with with Johnson about "Bishop Berkeley's ingenious sophistry to prove the non-existence of matter, and that every thing in the universe is merely ideal."

Johnson refutes this argument by kicking his foot against a rock.

Berkeley's argument is basically that we cannot prove the existence of the material world because our only evidence is found through our senses; but the senses are not necessary proof that something outside these senses exist.

He summarizes this argument at the beginning of Of the Principles of Human Knowledge:

"It is indeed an opinion strangely prevailing amongst men, that houses, mountains, rivers, and in a word all sensible objects, have an existence, natural or real, distinct from their being perceived by the understanding. But, with how great an assurance and acquiescence soever this principle may be entertained in the world, yet whoever shall find in his heart to call it in question may, if I mistake not, perceive it to involve a manifest contradiction. For, what are the forementioned objects but the things we perceive by sense? and what do we perceive besides our own ideas or sensations? and is it not plainly repugnant that any one of these, or any combination of them, should exist unperceived?"

-- George Berkeley, Of the Principles of Human Knowledge, Part I, sec. 4