Every obligation derives all sense and meaning; simply and solely from its relation to threatened punishment or promised reward. Hence, long before Kant was thought of, Locke says: "For since it would be utterly in vain, to suppose a rule set to the free actions of man, without annexing to it some enforcement of good and evil to determine his will; we must, wherever we suppose a law, suppose also some reward or punishment annexed to that law." (_Essay on the Human Understanding_, Bk. II., ch. 33, § 6). What =ought= to be done is therefore necessarily conditioned by punishment or reward; consequently, to use Kant's language, it is essentially and inevitably =hypothetical=, and never, as he maintains, =categorical=. If we think away these conditions, the conception of obligation becomes void of sense; hence absolute obligation is most certainly a _contradictio in adjecto._ A commanding voice, whether it come from within, or from without, cannot possibly be imagined except as threatening or promising. Consequently obedience to it, which may be wise or foolish according to circumstances, is yet always actuated by selfishness, and therefore morally worthless. The complete unthinkableness and nonsense of this conception of an =unconditioned obligation=, which lies at the root of the Kantian Ethics, appears later in the system itself, namely in the _Kritik der Praktischen Vernunft_: just as some concealed poison in an organism cannot remain hid, but sooner or later must come out and show itself. For this =obligation=, said to be so =unconditioned=, nevertheless postulates more than one condition in the background; it assumes a rewarder, a reward, and the immortality of the person to be rewarded.