From Kant's "On the Proverb: That May be True in Theory, But is of No Practical Use", 1793:

The complete equality of men as subjects in a nation is completely consistent with the greatest inequality in the quantity and degree of possessions they have, whether these be physical or mental superiority over others, or fortuitously acquired external goods, or, to speak generally, rights (of which there can be many) with respect to others. And, thus, the welfare of one very much depends on the will of another (that of the poor on that of the rich) � Nonetheless, as regards right�they are as subjects all equal to one another. For no one can coerce anyone else except through public law�but through this everyone else can resist him in the same way; no one can lose this authority to coerce�others except by breaking the law; and no one can renounce this right, i.e, no one can make a contract or perform some rightful act whereby he has no rights but only duties, for in so doing he would rob himself of the right to make a contract and would consequently cancel the contract itself.

From this idea of the equality of men as subjects in the commonwealth also comes this formula: Every member of the commonwealth must be permitted to attain any degree of status (to which a subject can aspire) to which his talent, his industry, and his luck may bring him; and his fellow subjects may not block his way by [appealing to] hereditary prerogatives (as the privilege belonging to a particular class) and thereby eternally hinder him and his descendants� no person can bequeath to his descendants the privilege of status he has within the commonwealth; nor, consequently, can anyone forcibly prevent them from attaining by virtue of their own merit even higher steps in the hierarchy� A person may bequeath everything else as long as it is material (and does not pertain to his person), for it can be acquired and disposed of by him as property, and thus a sequence of generations can bring about considerable inequality in financial circumstances among the members of a commonwealth (between wage earners and employers, and land-owners and agricultural workers, etc.). But a person is prevented from hindering others when their talent, industry, and good fortune make it possible for them to rise to circumstances equal to his. Otherwise a person would have to be able to coerce without being subject to coercive resistance from others, and that goes beyond the status of a fellow-subject. Except through some transgression of his own, no person who lives in the state of right obtaining in a commonwealth can lose this equality� for there is no act (neither his own nor that of another) that conforms with right whereby he can terminate his possession of himself and thus enter into the class of domestic animals, which can be used in any capacity one desires and can be kept in that state without their consent as long as one pleases, even given the restrictions (which is sometimes sanctioned by religion, as among the Indians) not to disfigure or kill them. A person�s state can be regarded as fortunate if only he is aware that his failure to rise to status equal to that of others is due to himself alone (his abilities or earnestness of will) or to circumstances for which he can blame no one else, and not because of the irresistible will of another. For in regard to rights, a person�s fellow-subjects in the commonwealth have no advantage over him.