But if Proudhon conceives all society in a mechanical manner, it is to be expected that he would again seek--and find--the same laws that he saw operating in the political constitution also in economic life. This is, as a matter of fact, the case. "Agreement solves every problem"; only agreement in economic life means with him exchange. "Social agreement," he says, "is in its essence like the agreement of exchange." Therefore the corner-stone in his economic system is exchange. But Proudhon transposed into this purely empiric idea a moral element, by presupposing equality and justice as necessary to exchange. Economic freedom, he reasons, is free exchange; but an exchange can only be called free which presupposes the equality of values, or, in other words, equality and justice. This again presupposes a just balance and constitution of values--a mutual balance of all economic and social forces. What, then, is economic freedom? It is equality and justice. And what is the opposite--the hindrance of these principles? It is inequality, injustice, slavery, which means property. This is the reason why Proudhon's doctrine of property stands at the centre of his system, which it by no means exhausts; it is the reason why he always proceeded from this point, and always returned to it again. Here we have clearly the reason for all his numberless and endless mistakes in the province of economics, the weak point of this otherwise great and noble mind. As we already have remarked about the _Contradictions_, Proudhon did not attack property in itself; he tried to ennoble it and bring it into harmony with the claims of justice and equality by taking away from it what to-day is a _jus utendi et abutendi_, that is, its rights over the substance of a thing, and the right of devolving it for ever. The ominous statement "Property is Theft" was directed only against this. This kind of property (_propriete_, _dominium_) was to be replaced by individual possession (_possession individuelle_): as to which one must take care to understand the distinction between "property" and "possession" in the legal sense.