Page:A Letter to Adam Smith on the Life, Death, and Philosophy of his friend David Hume (1777).djvu/55

 That the universe is nothing but a heap of perceptions, without a substance.

That though a man could bring himself to believe, yea, and have reason to believe, that every thing in the universe proceeds from some cause; yet it would be unreasonable for him to believe, that the universe itself proceeds from a cause.

That the perfection of human knowlege is to doubt.

That we ought to doubt of every thing, yea, of our doubts themselves, and therefore, the utmost that philosophy can do,