The most important of my discoveries have been suggested to me by my failures.

In the present state of our knowledge, it would be useless to attempt to speculate on the remote cause of the electrical energy... its relation to chemical affinity is, however, sufficiently evident. May it not be identical with it, and an essential property of matter?

You are now in a state in which a fly would be whose microscopic eye was changed to one similar to that of man: and you are wholly unable to associate what you see with your former knowledge.

When two elements combine and form more than one compound, the masses of one element that react with a fixed mass of the other are in the ratio of small whole numbers.

The wealth and prosperity of the country are only the comeliness of the body, the fullness of the flesh and fat; but the spirit is independent of them; it requires only muscle, bone and nerve for the true exercise of its functions. We cannot lose our liberty, because we cannot cease to think.

Profound minds are the most likely to think lightly of the resources of human reason, and it is the superficial thinker who is generally strongest in every kind of unbelief.

Experimental science hardly ever affords us more than approximations to the truth; and whenever many agents are concerned we are in great danger of being mistaken.

The ready apology covers a multitude of social sins.

The art galleries of Paris contain the finest collection of frames I ever saw.

The more we know, the more we feel our ignorance; the more we feel how much remains unknown.