As to permissive laws, these are inconceivable side by side with the imperative or prohibitive, not indeed because no law ever permits, but because by the very fact that those are imperative or prohibitive, they are at the same time permissive: every _jubeo_ or _veto_ is at the same time a _permitto._ Principles, as universal volitions, never permit, because nothing escapes their command; but a single volitional act, affirming itself, does not exclude for that reason the possibility that other volitional acts, indeed infinite acts, should be affirmed; for the singular never exhausts its universal. And laws are volitions of class, they impose groups of single acts--groups that are more or less rich, but always contingent: hence a law always leaves all the other actions and classes of action that can be the object of will unwilled (that is, neither commanded nor prohibited), and, therefore, _permitted._ And even if we take all the laws formulated up to a given moment, all together they do not exhaust the universal; and if new laws be accumulated, one upon the other, be divided and split up "with panting breath," to obtain complete exhaustion, a _progressus in infinitum_ will certainly be attained, but never exhaustion, which is unattainable. This amounts to saying that outside law or laws, there is always _the permitted, the lawful, the indifferent, the privilege, the right,_ or whatever be termed the concept correlative to that of command, veto, or duty, a duality of terms that expresses the _finitude_ of law; hence, when a determined privilege, a determined legal right, a determined right, has been annulled by a new law, when something previously indifferent has been differentiated, privilege, the permitted, the indifferent, right, always arise from the bosom of the new law. [Sidenote: _Mutability of laws._] Another contingent character of the content of laws is their _mutability._ Laws are changeable, whereas principles, or laws of the universal content, are unchangeable, and ready to give form to all the most various historical material. Since actual conditions are constantly changing, it is necessary to add new laws to the old, to retouch and correct these, or to abolish them altogether. This is to be seen equally in the programmes of individual lives, as in the programmes of social and political laws. [Sidenote: _Empirical concepts as to the modes of change._]