George Berkeley

Esse est percipi (To be is to be perceived).

All the choir of heaven and furniture of the earth, in a word, all those bodies which compose the mighty frame of the world, have not any subsistence without a mind.

Some truths there are so near and obvious to the mind, that a man need only open his eyes to see them.

The only thing whose existence I deny is that which philosophers call matter or corporeal substance.

Sensible things are those only which are immediately perceived by sense.

It is 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.

To say there is a substance without any quality is to say there is nothing.

The ideas of sense are more strong, lively, and distinct than those of the imagination; they have likewise a steadiness, order, and coherence, and are not excited at random, as those which are the effects of human wills often are, but in a regular train or series, the admirable connexion whereof sufficiently testifies the wisdom and benevolence of its Author.

Truth is the cry of all, but the game of few.

We are not to think that these ideas are useless; because they are not the originals of things, but only the copies.

The being of an idea consists in being perceived.

I am of a vulgar cast, and think as the crowd, that the objects we see and feel, are nothing but those very things which we perceive by sense.

The table I write on, I say, exists, that is, I see and feel it; and if I were out of my study I should say it existed, meaning thereby that if I was in my study I might perceive it, or that some other spirit actually does perceive it.

You may, if you please, make a distinction between the two, but you will find it to be a distinction without a difference.

I am content to put the whole upon this issue; if you can conceive it possible for any sensible object whatever to exist without the mind, then I grant it actually to exist without the mind.

The objects of sense exist only in the mind.

It is plain that the very notion of what is called Matter or corporeal substance, involves a contradiction in it.

The only substance is spirit, that which perceives.

We are not to attribute any real existence to these secondary qualities, as they are called, but only to the primary.

The existence of an unthinking substance, or of matter, is not only impossible, but also useless.