According to Kant, this principle or law yields, or is conjoint with, a “permissive law” or “juridical postulate” of practical reason, which gives to everyone the right of property in any of the things of the world.
In Kant’s view, all the non-human things of the world are at the disposal of humanity as a whole. Our freedom to own/use them can be restricted in the light of practical reason’s a priori formal, universal law of right/justice, to which all positive, juridical laws must conform.
Anyone who first occupies or possesses a piece of land, for instance, must be assumed to be doing so as part of humanity’s “external freedom” in accordance with practical reason’s a priori-formal law of right.
Since the first acquisition of land or things of the world affects the freedom of action of everyone else, its full moral justification cannot rest on a mere unilateral action. According to Kant, therefore, the moral legitimacy of any original appropriation of property remains provisional until it is ratified by a universal agreement of all who are affected by it.
Only such a universal agreement of all who are affected by the original appropriations of property can fulfil the requirement of the Universal Principle of Right/Justice! It is towards the realisation of this ideal requirement of universal Right or Justice that Kant offers his “social contract conceptualisation” of the state and of a “pacific union” of states on a global level.
He speaks of the state as “a union of a multitude of men under laws of Right.” Describing the social contract as an idea of reason (rather than as an event), i.e. as an analogue of reason’s Categorical imperative, Kant writes:
The act by which people forms itself into a state is the original contract. Properly speaking, the original contract is only the idea of this act, in terms of which alone we can think of the legitimacy of a state. In accordance with the original contract, everyone within people gives up his external freedom in order to take it up again immediately as a member of a commonwealth that is, of a people considered as a state.
It is in fact merely an idea of reason, which nonetheless has undoubted practical reality; for it can oblige every legislator to frame his laws in such a way that they * could have been produced by the united will of a whole nation, and to regard each subject, in so far as he can claim citizenship, as if he had consented with the general will.
The reason or motivation, which Kant gives for the social contract, is different from the reasons given by Hobbes and Locke. The motivations they give is rational self-interest and the fear of violent death (Hobbes) or the natural right to self-preservation and the protection of property rights (Locke).
For Kant, the motivation for the contract is to secure a rational right to property, whereby the contractors could, with moral justification, exclude others from access to it, to which they (i.e. the contractors) only had a provisional right in the state of nature. He writes:
From private right in the natural condition there now arises the postulate of public right: In relation to an unavoidable coexistence with others, you should make the transition from the state of nature to a juridical state, i.e., one of distributive justice, Kant, unlike Hobbes or Locke, thinks of the institution of property as inseparable from the civil state. He writes:
But the state of, a legislative, universal and truly united will is the civil state. Therefore, something external can be originally acquired only in conformity with the idea of a civil state, that is, in reference to it and its realisation, though before its reality.
According to Hobbes, property rights are created by the sovereign state, which is assumed to be independent from property. For Locke, property rights in the state of nature are absolute. They are, so to say, independent from the state, which only has to guarantee and protect those “natural rights.”
For Kant, there can be no absolute natural rights to property, just as there is no state that is independent from property. Our right to property, says Kant, can only be legitimate or just if it is in accordance with the Universal Principle of Right/Justice. Our property rights can therefore be only provisional until they are ratified both by a civil state and by a peaceful confederation of nations/states of the world.