That food nourishes, sleep refreshes, and fire warms us; that to sow in the seed-time is the way to reap in the harvest, and, in general, that to obtain such or such ends, such or such means are conducive, all this we know, not by discovering any necessary connexion between our ideas, but only by the observation of the settled laws of nature, without which we should be all in uncertainty and confusion, and a grown man no more know how to manage himself in the affairs of life than an infant just born.

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?

How often must I repeat, that I know or am conscious of my own being; and that I myself am not my ideas, but somewhat else, a thinking, active principle that perceives, knows, wills, and operates about ideas?

The most ingenious men are now agreed, that [universities] are only nurseries of prejudice, corruption, barbarism, and pedantry.

The real essence, the internal qualities, and constitution of even the meanest object, is hid from our view; something there is inevery drop of water, every grain of sand, which it is beyond the power of human understanding to fathom or comprehend. But it is evidentthat we are influenced by false principles to that degree as to mistrust our senses, and think we know nothing of those things which we perfectly comprehend.

[Christianity] neither enjoins the nastiness of the Cynic, nor the insensibility of the Stoic.

But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park [. . .] and nobody by to perceive them. [...] The objects of sense exist only when they are perceived; the trees therefore are in the garden [. . .] no longer than while there is somebody by to perceive them.