That neither our thoughts, nor passions, nor ideas formed by the imagination, exist without the mind, is what every body will allow.

What doubts, what hypotheses, what labyrinths of amusement, what fields of disputation, what an ocean of false learning, may be avoided by that single notion of immaterialism!

To be is to be perceived (Esse est percipi)." Or, "If a tree falls in the forest and no one is there to hear it, does it make a sound?

If what you mean by the word "matter" be only the unknown support of unknown qualities, it is no matter whether there is such a thing or no, since it no way concerns us; and I do not see the advantage there is in disputing about what we know not what, and we know not why.

I do not deny the existence of material substance merely because I have no notion of it, but because the notion of it is inconsistent, or in other words, because it is repugnant that there should be a notion of it.

That neither our thoughts, nor passions, nor ideas formed by the imagination, exist without the mind, is what every body will allow.

A mind at liberty to reflect on its own observations, if it produce nothing useful to the world, seldom fails of entertainment to itself.