Nothing is demonstrable, unless the contrary implies a contradiction. Nothing, that is distinctly conceivable, implies a contradiction. Whatever we conceive as existent, we can also conceive as non-existent. There is no being, therefore, whose non-existence implies a contradiction. Consequently there is no being, whose existence is demonstrable.
David HumeNo amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion.
David HumeTho' there be no such Thing as Chance in the World; our Ignorance of the real Ccause of any Event has the same Influence on the Understanding, and begets a like Species of Belief or Opinion.
David HumeThe conduct of a man, who studies philosophy in this careless manner, is more truly sceptical than that of any one, who feeling inhimself an inclination to it, is yet so over-whelm'd with doubts and scruples, as totally to reject it. A true sceptic will be diffident of his philosophical doubts, as well as of his philosophical conviction; and will never refuse any innocent satisfaction, which offers itself, upon account of either of them.
David Hume