- The ambition of empiricism is to reduce all relevant matters of fact to sensory qualities.
- Sensory qualities, even if assumed that they can be known immediately, do not justify matters of fact outside sensory qualities.
- The ambition of empiricism to reduce all matters of fact outside sensory qualities to sensory qualities is impossible.
I vividly dream I am on a beach when I am not in fact on a beach. There is no ocean, no smell of the sea, no sound of gulls flying overhead. The beer I’ve just drunk is, unfortunately, not actually a beer. My sensory qualities say nothing about matters of fact outside sensory qualities.
The hypothetical scenario of the vivid dream is designed solely to demonstrate that the existence of any and all matters of fact outside sensory qualities is not deductively entailed by sensory qualities. What we have is a variation on the problem of underdetermination: the available data (sensory qualities) do not permit us to make a decision between two rival theories.
In response to my positing of a vivid dream, a defender of empiricism might argue that I naturally dream about things I’ve otherwise experienced. In response, I will happily admit that there have been some times in the past when I have experienced sensory qualities of lounging on beaches. What of it? It’s far too easy to change the hypothetical scenario in any way I choose to deal with any assumption the defender makes. No matter the objection, a small nudge to the scenario means I cannot tell apart a dream from waking life, meaning sensory qualities do not justify matters of fact outside sensory qualities.
Of course, I know I live in an objective reality — but does empiricism justify such a basic intuition? Hume and Berkeley thought not, and that any attempt to pull empiricism’s irons out of the fire was doomed to failure: If sensory qualities are not necessarily caused by matters of fact, but caused by imaginative creations of the mind, then how can I determine the causal relationship in any case? By appealing to sensory qualities? Such an attempt would, of course, beg the question.
After we came out of the church, we stood talking for some time together of Bishop Berkeley’s ingenious sophistry to prove the nonexistence of matter, and that every thing in the universe is merely ideal. I observed, that though we are satisfied his doctrine is not true, it is impossible to refute it. I never shall forget the alacrity with which Johnson answered, striking his foot with mighty force against a large stone, till he rebounded from it — ‘I refute it thus.’ (James Boswell: A Life of Samuel Johnson)