Cogitatio in vero exquirendo maxime versatur. Appetitus impellit ad agendum.
The Intellect engages us in the pursuit of Truth. The Passions impel us to Action.

As soon as questions of will or decision or reason or choice of action arise, human science is at a loss.

Concern should drive us into action, not into a depression.

Confucius once said that a bear could not fart at the North Pole without causing a big wind in Chicago.
By this he meant that all events, therefore, all men, are interconnected in an unbreakable web. What man does, no matter how seemingly insignificant, vibrates through the strands and affects every man.

Do, or do not. There is no try.

For this we must make automatic and habitual, as early as possible, as many useful actions as we can, and guard against the growing into ways that are likely to be disadvantageous to us, as we should guard against the plague?

If it were possible for us to have so deep an insight into a man's character as shown both in inner and in outer actions, that every, even the least, incentive to these actions and all external occasions which affect them were so known to us that his future conduct could be predicted with as great a certainty as the occurrence of a solar or lunar eclipse, we could nevertheless still assert that the man is free.

If the human race ever stops acting on the basis of what it thinks it knows, paralyzed by fear that its knowledge may be wrong, then Homo sapiens will be making its application for membership in the dinosaur club.

In fact, whenever energy is transmitted from one body to another in time, there must be a medium or substance in which the energy exists after it leaves one body and before it reaches the other ... and if we admit this medium as an hypothesis, I think it ought to occupy a prominent place in our investigations, and that we ought to endeavour to construct a mental representation of all the details of its action, and this has been my constant aim in this treatise.

Once human beings realize something can be done, they're not satisfied until they've done it.

The end of knowledge is power ... the scope of all speculation is the performing of some action or thing to be done.

The great end of life is not knowledge but action.
[In the same time period, Karl Marx made a similar statement.]

The instinct to command others, in its primitive essence, is a carnivorous, altogether bestial and savage instinct. Under the influence of the mental development of man, it takes on a somewhat more ideal form and becomes somewhat ennobled, presenting itself as the instrument of reason and the devoted servant of that abstraction, or political fiction, which is called the public good. But in its essence it remains just as baneful, and it becomes even more so when, with the application of science, it extends its scope and intensifies the power of its action. If there is a devil in history, it is this power principle.

The world was full of locked doors, and he had to get his hand on every key.

There are no mistakes. The events we bring upon ourselves, no matter how unpleasant, are necessary in order to learn what we need to learn; whatever steps we take, they're necessary to reach the places we've chosen to go.

Thus the system of the world only oscillates around a mean state from which it never departs except by a very small quantity. By virtue of its constitution and the law of gravity, it enjoys a stability that can be destroyed only by foreign causes, and we are certain that their action is undetectable from the time of the most ancient observations until our own day. This stability in the system of the world, which assures its duration, is one of the most notable among all phenomena, in that it exhibits in the heavens the same intention to maintain order in the universe that nature has so admirably observed on earth for the sake of preserving individuals and perpetuating species.