But it does not follow that this distinction between the principle of happiness and that of morality is an opposition between them, and pure practical reason does not require that we should renounce all claim to happiness, but only that the moment duty is in question we should take no account of happiness.It may even in certain respects be a duty to provide for happiness; partly, because (including skill, wealth, riches) it contains means for the fulfilment of our duty; partly, because the absence of it (e.g., poverty) implies temptations to transgress our duty.But it can never be an immediate duty to promote our happiness, still less can it be the principle of all duty.Now, as all determining principles of the will, except the law of pure practical reason alone (the moral law), are all empirical and, therefore, as such, belong to the principle of happiness, they must all be kept apart from the supreme principle of morality and never be incorporated with it as a condition; since this would be to destroy all moral worth just as much as any empirical admixture with geometrical principles would destroy the certainty of mathematical evidence, which in Plato's opinion is the most excellent thing in mathematics, even surpassing their utility.
Instead, however, of the deduction of the supreme principle of pure practical reason, that is, the explanation of the possibility of such a knowledge a priori, the utmost we were able to do was to show that if we saw the possibility of the freedom of an efficient cause, we should also see not merely the possibility, but even the necessity, of the moral law as the supreme practical law of rational beings, to whom we attribute freedom of causality of their will;because both concepts are so inseparably united that we might define practical freedom as independence of the will on anything but the moral law.But we cannot perceive the possibility of the freedom of an efficient cause, especially in the world of sense; we are fortunate if only we can be sufficiently assured that there is no proof of its impossibility, and are now, by the moral law which postulates it, compelled and therefore authorized to assume it.However, there are still many who think that they can explain this freedom on empirical principles, like any other physical faculty, and treat it as a psychological property, the explanation of which only requires a more exact study of the nature of the soul and of the motives of the will, and not as a transcendental predicate of the causality of a being that belongs to the world of sense (which is really the point).They thus deprive us of the grand revelation which we obtain through practical reason by means of the moral law, the revelation, namely, of a supersensible world by the realization of the otherwise transcendent concept of freedom, and by this deprive us also of the moral law itself, which admits no empirical principle of determination.Therefore it will be necessary to add something here as a protection against this delusion and to exhibit empiricism in its naked superficiality.
The notion of causality as physical necessity, in opposition to the same notion as freedom, concerns only the existence of things so far as it is determinable in time, and, consequently, as phenomena, in opposition to their causality as things in themselves.Now if we take the attributes of existence of things in time for attributes of things in themselves (which is the common view), then it is impossible to reconcile the necessity of the causal relation with freedom; they are contradictory.For from the former it follows that every event, and consequently every action that takes place at a certain point of time, is a necessary result of what existed in time preceding.Now as time past is no longer in my power, hence every action that Iperform must be the necessary result of certain determining grounds which are not in my power, that is, at the moment in which I am acting I am never free.Nay, even if I assume that my whole existence is independent on any foreign cause (for instance, God), so that the determining principles of my causality, and even of my whole existence, were not outside myself, yet this would not in the least transform that physical necessity into freedom.For at every moment of time I am still under the necessity of being determined to action by that which is not in my power, and the series of events infinite a parte priori, which I only continue according to a pre-determined order and could never begin of myself, would be a continuous physical chain, and therefore my causality would never be freedom.
If, then, we would attribute freedom to a being whose existence is determined in time, we cannot except him from the law of necessity as to all events in his existence and, consequently, as to his actions also; for that would be to hand him over to blind chance.Now as this law inevitably applies to all the causality of things, so far as their existence is determinable in time, it follows that if this were the mode in which we had also to conceive the existence of these things in themselves, freedom must be rejected as a vain and impossible conception.Consequently, if we would still save it, no other way remains but to consider that the existence of a thing, so far as it is determinable in time, and therefore its causality, according to the law of physical necessity, belong to appearance, and to attribute freedom to the same being as a thing in itself.
This is certainly inevitable, if we would retain both these contradictory concepts together; but in application, when we try to explain their combination in one and the same action, great difficulties present themselves which seem to render such a combination impracticable.
