The pit of a theatre is the one place where the tears of virtuous and wicked men alike are mingled.

The following general definition of an animal: a system of different organic molecules that have combined with one another, under the impulsion of a sensation similar to an obtuse and muffled sense of touch given to them by the creator of matter as a whole, until each one of them has found the most suitable position for it shape and comfort.

In order to shake a hypothesis, it is sometimes not necessary to do anything more than push it as far as it will go.

There are three principal means of acquiring knowledge available to us: observation of nature, reflection, and experimentation. Observation collects facts; reflection combines them; experimentation verifies the result of that combination. Our observation of nature must be diligent, our reflection profound, and our experiments exact. We rarely see these three means combined; and for this reason, creative geniuses are not common.

Are we not madder than those first inhabitants of the plain of Sennar? We know that the distance separating the earth from the sky is infinite, and yet we do not stop building our tower.

If exclusive privileges were not granted, and if the financial system would not tend to concentrate wealth, there would be few great fortunes and no quick wealth. When the means of growing rich is divided between a greater number of citizens, wealth will also be more evenly distributed; extreme poverty and extreme wealth would be also rare.

The purpose of an encyclopedia is to collect knowledge disseminated around the globe; to set forth its general system to the men with whom we live, and transmit it to those who will come after us, so that the work of preceding centuries will not become useless to the centuries to come; and so that our offspring, becoming better instructed, will at the same time become more virtuous and happy, and that we should not die without having rendered a service to the human race in the future years to come

Go further, and require each of them to make a contribution: you will see how many things are still missing, and you will be obliged to get the assistance of a large number of men who belong to different classes, priceless men, but to whom the gates of the academies are nonetheless closed because of their social station. All the members of these learned societies are more than is needed for a single object of human science; all the societies together are not sufficient for a science of man in general.

Reason is to the philosopher what grace is to the Christian.Grace causes the Christian to act, reason the philosopher. Other men are carried away by their passions, their actions not being preceded by reflection: these are the men who walk in darkness. On the other hand, the philosopher, even in his passions, acts only after reflection; he walks in the dark, but by a torch. The philosopher forms his principles from an infinity of particular observations. Most people adopt principles without thinking of the observations that have produced them, they believe the maxims exist, so to speak, by themselves. But the philosopher takes maxims from their source; he examines their origin; he knows their proper value, and he makes use of them only in so far as they suit him. Truth is not for the philosopher a mistress who corrupts his imagination and whom he believes to be found everywhere; he contents himself with being able to unravel it where he can perceive it. He does not confound it with probability; he takes for true what is true, for false what is false, for doubtful what is doubtful, and probable what is only probable. He does more, and here you have a great perfection of the philosopher: when he has no reason by which to judge, he knows how to live in suspension of judgment... The philosophical spirit is, then, a spirit of observation and exactness, which relates everything to true principles...

The good of the people must be the great purpose of government. By the laws of nature and of reason, the governors are invested with power to that end. And the greatest good of the people is liberty. It is to the state what health is to the individual.