According to the materialist conception of history, the ultimately determining element in history is the production and reproduction of real life.

— Friedrich Engels

All history has been a history of class struggles between dominated classes at various stages of social development.

— Friedrich Engels

An ounce of action is worth a ton of theory.

— Friedrich Engels

Capitalist production...was necessary to develop the productive forces of society to a level which will make possible an equal development worthy of human beings for all members of society. All earlier forms of society were too poor for this.

— Friedrich Engels

Freedom is the recognition of necessity.

— Friedrich Engels

If there were no Frenchwomen, life wouldn't be worth living.

— Friedrich Engels

...in pure mathematics the mind deal only with its own creations and imaginations. The concepts of number and form have not been derived from any source other than the world of reality. The ten fingers on which men learned to count, that is, to carry out the first arithmetical operation, may be anything else, but they are certainly not only objects that can be counted, but also the ability to exclude all properties of the objects considered other than their number-and this ability is the product of a long historical evolution based on experience. Like the idea of number, so the idea of form is derived exclusively from the external world, and does not arise in the mind as a product of pure thought.

— Friedrich Engels

In short, the Communists everywhere support every revolutionary movement against the existing social and political order of things. In all these movements they bring to the front, as the leading question in each, the property question, no matter what its degree of development at the time. Finally, they labor everywhere for the union and agreement of the democratic parties of all countries. The Communists disdain to conceal their views and aims. They openly declare that their ends can be attained only by the forcible overthrow of all existing social conditions. Let the ruling classes tremble at a Communistic revolution. The proletarians have nothing to lose but their chains. They have a world to win. WORKING MEN OF ALL COUNTRIES, UNITE!

— Friedrich Engels

In the second place, however, history is made in such a way that the final result always arises from conflicts between many individual wills, of which each in turn has been made what it is by a host of particular conditions of life. Thus, there are innumerable intersecting forces, an infinite series of parallelograms of forces which give rise to one resultant — the historical event. This may again itself be viewed as the product of a power which works as a whole unconsciously and without volition. For what all individual wills is obstructed by everyone else, and what emerges is something that no one willed. Thus, history has proceeded hitherto in the manner of a natural process and is essentially subject to the same laws of motion. But from the fact that the wills of individuals — each of whom desires what he is impelled to by his physical constitution and external, in the last resort economic, circumstances (either his own personal circumstances or those of society in general) — do not attain what they want, but are merged into an aggregate mean, a common resultant, it must not be concluded that they are equal to zero. On the contrary, each contributes to the resultant and is to this extent included in it.

— Friedrich Engels

Just as Darwin discovered the law of development of organic nature, so Marx discovered the law of development of human history: the simple fact, hitherto concealed by an overgrowth of ideology, that mankind must first eat, drink, have shelter and clothing, before it can pursue politics, science, art, religion, etc.

— Friedrich Engels