Duty! Sublime and mighty name that embraces nothing charming or insinuating but requires submission, and yet does not seek to move the will by threatening anything that would arouse natural aversion or terror in the mind but only holds forth a law that of itself finds entry into the mind and yet gains reluctant reverence (though not always obedience), a law before which all inclinations are dumb, even though they secretly work against it; what origin is there worthy of you, and where is to be found the root of your noble descent which proudly rejects all kinship with the inclinations, descent from which is the indispensable condition of that worth which human beings alone can give themselves?
This quote encapsulates Kant's view of moral motivation. Acting from duty is set apart completely from all other ways of acting, which are taken to spring from mere "inclination." Moral action must spring solely from the motive of duty, not fear of punishment, hope of reward, or any other reason other than pure dutifulness. In Kant's view, non-moral motivation is always driven by self-love. When I am not acting on duty, I am trying to bring about one of my desires, say, a desire to achieve a reward from God, or to avoid a punishment from him. What lies behind my attempt to bring about my desire is an attempt to bring about the satisfaction of my desire, that is, to bring about the pleasure of having satisfied the desire. Only action from dutifulness is not in the end a means of pleasing oneself. This is reflective of how acting from duty has a different origin metaphysically from other ways of acting: acting from duty is action caused from the noumenal realm. That moral actions are not motivated by desire is the negative way of understanding our freedom when we act morally; that they are caused by the noumenal is the positive way of understanding that freedom.
FUNDAMENTAL LAW OF PURE PRACTICAL REASON: So act that the maxim of your will could always hold at the same time as a principle in a giving of universal law.
This quote is Kant's famous categorical imperative. In the Analytic, this, the one ultimate ethical principle, is derived. The proof distinguishes the form of a law, which is that it is universally applicable, from its matter, what in particular it tells us to do. It then argues that if the matter is anything beyond an expression of the form, the law is no law, for obeying any such material principle would be heteronomous. The categorical imperative, or law of pure practical reason, is the only law we can follow and still be acting appropriately freely. This principle says that we can morally assess an action by imagining everyone in the world acting on its motive. If this thought is coherent, the action is right; if not, it is wrong. If a person commits suicide when he is tired of life, this is wrong, for if everyone disposed of his life so casually, the society the suicide depended on while the man lived would collapse. Similarly, if everyone refused to give charity, society would collapse. If everyone told lies, no one would be believed, so the very act of lying would be impossible; therefore, lying is not universalizeable, and so it is wrong.
Two things fill the mind with ever new and increasing admiration and reverence, the more often and more steadily one reflects on them: the starry heavens above me and the moral law within me.
Kant compares the physical and the moral sciences. Both start from self-evidence sources of wonder. Although both are right before us, though, a true understanding of either is not easy to find. Both have been lost for a long time in superstition and blind conjecture. The physical sciences have finally reached a point where they are developing rationally. The moral sciences have not reached that point yet, but Kant hopes to pioneer a scientific, rational approach to ethics in his work. The method Kant uses in the Analytic, which imitates that of a geometrical treatise, both reflects this optimism and is meant to further this rationalizing of ethics. By carefully separating off the a priori foundations of ethics from anything empirical, and then proceeding through a series of proofs to the most fundamental moral principle, Kant hopes to improve on the method of doing ethics. Later, the application of this principle can be spelled out by looking at the empirical world. To look at the empirical world while pulling out the fundamental principle, though, he regards as fatal to clarity and rigor.
[H]ow can that mean be called quite free at the same point of time and in regard to the same action in which and in regard to which he is nevertheless subject to an unavoidable nature necessity? It is a wretched subterfuge to seek to evade this by saying that the kind of determining grounds of his causality in accordance with natural law agrees with a comparative concept of freedom (according to which that is sometimes called a free effect, the determining natural ground of which lies within the acting being, e.g., that which a projectile accomplishes when it is in free motion )
Some people think that freedom and determinism are compatible. The most promising way of pursuing this idea is to compare interrupted behavior with behavior that is allowed to develop without interference. We can agree that shackles prevent a person from being free, regardless of the truth or falsity of determinism, because they prevent his intentions from being expressed in the world. So, the person who takes freedom and determinism to be compatible may hold that a person can be free if he can express his intention in action with no interference, even if his mental state is determined by the past and it, in turn, determines his actions. Kant claims that on their view, a projectile or a clock is free, for it, too, can sometimes act without interference. To Kant, this is absurd. The only alternative, if one believes in both determinism and freedom, is to take freedom as causation from the noumenal realm, where determinism does not apply.
These postulates are not theoretical dogmas but presuppositions having a necessarily practical reference and thus, although they do not indeed extend speculative cognition, they give objective reality to the ideas of speculative reason in general (by means of their reference to what is practical) and justify its holding concepts even the possibility of which it could not otherwise presume to affirm.
Theoretical reason, we learn in the first Critique, cannot inform us as to the existence of God, freedom, and immortality. However, following pure practical reason requires that we assume that these things are real. So we have reason to believe in them. (Freedom has a special role among the postulates of pure practical reason in that we can also non-sensorily detect it when we non- sensorily detect the moral law.) The reason why we must believe in the postulates is the linkage of practical reason and the good. Although action from practical reason is always motivated solely by dutifulness, it also aims always at the highest good. The highest good is the rewarding of the virtuous with happiness, so it looks like we cannot assume that acting dutifully will produce the highest good. If this were right, we could make no sense of acting morally. However, if we assume that there is an afterlife and that God will reward or punish us there in accordance with our goodness or badness, then acting dutifully can aim at the highest good, and morality is possible.