Some excerpts from Kant’s Groundwork of the Metaphysics of Morals (translated by Thomas Abbot) with some explanations by Tom Atchison



1.  In a famous passage at the beginning of the Groundwork of the Metaphysics of Morals, Kant claims that nothing is “good without qualification” except a “good will.”  He then discusses a variety of “talents of the mind” and “qualities of temperament,” arguing that none of them is good in itself (without a good will).  Do you think he’s right?  Here is Kant (in translation, of course):


Nothing can possibly be conceived in the world, or even out of it, which can be called good, without qualification, except a good will. Intelligence, wit, judgment, and the other talents of the mind, however they may be named, or courage, resolution, perseverance, as qualities of temperament, are undoubtedly good and desirable in many respects; but these gifts of nature may also become extremely bad and mischievous if the will which is to make use of them, and which, therefore, constitutes what is called character, is not good. It is the same with the gifts of fortune. Power, riches, honor, even health, and the general well-being and contentment with one's condition which is called happiness, inspire pride, and often presumption, if there is not a good will to correct the influence of these on the mind, and with this also to rectify the whole principle of acting and adapt it to its end. The sight of a being who is not adorned with a single feature of a pure and good will, enjoying unbroken prosperity, can never give pleasure to an impartial rational spectator. Thus a good will appears to constitute the indispensable condition even of being worthy of happiness.

There are even some qualities which are of service to this good will itself and may facilitate its action, yet which have no intrinsic unconditional value, but always presuppose a good will, and this qualifies the esteem that we justly have for them and does not permit us to regard them as absolutely good. Moderation in the affections and passions, self-control, and calm deliberation are not only good in many respects, but even seem to constitute part of the intrinsic worth of the person; but they are far from deserving to be called good without qualification, although they have been so unconditionally praised by the ancients. For without the principles of a good will, they may become extremely bad, and the coolness of a villain not only makes him far more dangerous, but also directly makes him more abominable in our eyes than he would have been without it.


2.  Kant insists that a good will is good ‘in itself’ and not because of the results it produces.  He seems to think that what is admirable is trying to do the right thing, regardless of whether you succeed.  He says:


A good will is good not because of what it performs or effects, not by its aptness for the attainment of some proposed end, but simply by virtue of the volition [a 'volition' is an 'act of will', a 'willing']; that is, it is good in itself, and considered by itself is to be esteemed much higher than all that can be brought about by it in favour of any inclination, nay even of the sum total of all inclinations. Even if it should happen that, owing to special disfavour of fortune, or the stingy provision of a step-motherly nature, this will should wholly lack power to accomplish its purpose, if with its greatest efforts it should yet achieve nothing, and there should remain only the good will (not, to be sure, a mere wish, but the summoning of all means in our power), then, like a jewel, it would still shine by its own light, as a thing which has its whole value in itself. Its usefulness or fruitfulness can neither add nor take away anything from this value. It would be, as it were, only the setting to enable us to handle it the more conveniently in common commerce, or to attract to it the attention of those who are not yet connoisseurs, but not to recommend it to true connoisseurs, or to determine its value.



3.  What does Kant mean by a ‘good will’, anyway?  It has to do with ‘duty’.  He develops a distinction between acting in conformity with duty and acting from the motive of duty.  To have a good will it is not enough to do the right thing.  We have to do it because it is the right thing.  His examples try to bring out the fact that we often have a variety of motives for our actions and that it is only in fairly unusual circumstances that we can be sure that we are acting ‘from duty’ and not ‘from inclination’.  “Inclination” in Kant’s vocabulary means something like ‘want’ or ‘desire’.  It’s not wrong to treat other people kindly, for example, because you like them and want to please them or because you want them to like you and hope to obtain some benefit from them.  But acting from motives like these is not particularly admirable, either.  What is genuinely admirable – what has true ‘moral worth’ – is to treat other people well when you don’t like them and when you have nothing to gain. He gives a number of examples:


For example, it is always a matter of duty that a dealer should not over charge an inexperienced purchaser; and wherever there is much commerce the prudent tradesman does not overcharge, but keeps a fixed price for everyone, so that a child buys of him as well as any other. Men are thus honestly served; but this is not enough to make us believe that the tradesman has so acted from duty and from principles of honesty: his own advantage required it; it is out of the question in this case to suppose that he might besides have a direct inclination in favour of the buyers, so that, as it were, from love he should give no advantage to one over another. Accordingly the action was done neither from duty nor from direct inclination, but merely with a selfish view.

On the other hand, it is a duty to maintain one's life; and, in addition, everyone has also a direct inclination to do so. But on this account the often anxious care which most men take for it has no intrinsic worth, and their maxim has no moral import. They preserve their life as duty requires, no doubt, but not because duty requires. On the other band, if adversity and hopeless sorrow have completely taken away the relish for life; if the unfortunate one, strong in mind, indignant at his fate rather than desponding or dejected, wishes for death, and yet preserves his life without loving it- not from inclination or fear, but from duty- then his maxim has a moral worth.

To be beneficent when we can is a duty; and besides this, there are many minds so sympathetically constituted that, without any other motive of vanity or self-interest, they find a pleasure in spreading joy around them and can take delight in the satisfaction of others so far as it is their own work. But I maintain that in such a case an action of this kind, however proper, however amiable it may be, has nevertheless no true moral worth, but is on a level with other inclinations, e.g., the inclination to honor, which, if it is happily directed to that which is in fact of public utility and accordant with duty and consequently honorable, deserves praise and encouragement, but not esteem. For the maxim lacks the moral import, namely, that such actions be done from duty, not from inclination. Put the case that the mind of that philanthropist were clouded by sorrow of his own, extinguishing all sympathy with the lot of others, and that, while he still has the power to benefit others in distress, he is not touched by their trouble because he is absorbed with his own; and now suppose that he tears himself out of this dead insensibility, and performs the action without any inclination to it, but simply from duty, then first has his action its genuine moral worth. Further still; if nature has put little sympathy in the heart of this or that man; if he, supposed to be an upright man, is by temperament cold and indifferent to the sufferings of others, perhaps because in respect of his own he is provided with the special gift of patience and fortitude and supposes, or even requires, that others should have the same- and such a man would certainly not be the meanest product of nature- but if nature had not specially framed him for a philanthropist, would he not still find in himself a source from whence to give himself a far higher worth than that of a good-natured temperament could be? Unquestionably. It is just in this that the moral worth of the character is brought out which is incomparably the highest of all, namely, that he is beneficent, not from inclination, but from duty.

… It is in this manner, undoubtedly, that we are to understand those passages of Scripture in which we are commanded to love our neighbour, even our enemy. For love, as an affection, cannot be commanded, but beneficence for duty's sake may; even though we are not impelled to it by any inclination- nay, are even repelled by a natural and unconquerable aversion. This is practical love and not pathological- a love which is seated in the will, and not in the propensions of feeling- in principles of action and not of tender sympathy; and it is this love alone which can be commanded.  [“Pathological” here does not mean abnormal or diseased.  It’s meaning is closer to the Greek pathos “something one suffers or which happens to one” (as opposed to something one actively does).  Feelings just happen; we can’t control how we feel; so it makes no sense to command people to love, if love is a feeling.]



4)      Next Kant begins to explain his famous “Categorical Imperative” – the moral law that tells us what duty requires.  If you read this section carefully, I think you will see that the basic idea is the one expressed by the familiar question, “What if everyone did that?”  Note: Kant uses the term "maxim" to mean "a rule of conduct."  He is thinking that, whenever I act, I am acting for some reason, and that reason implies a rule.  He says:


But what sort of law can that be, the conception of which must determine the will, even without paying any regard to the effect expected from it, in order that this will may be called good absolutely and without qualification? As I have deprived the will of every impulse which could arise to it from obedience to any law, there remains nothing but the universal conformity of its actions to law in general, which alone is to serve the will as a principle, i.e., I am never to act otherwise than so that I could also will that my maxim should become a universal law. Here, now, it is the simple conformity to law in general, without assuming any particular law applicable to certain actions, that serves the will as its principle and must so serve it, if duty is not to be a vain delusion and a chimerical notion. The common reason of men in its practical judgments perfectly coincides with this and always has in view the principle here suggested.

Let the question be, for example: May I when in distress make a promise with the intention not to keep it? I readily distinguish here between the two significations which the question may have: Whether it is prudent, or whether it is right, to make a false promise? The former may undoubtedly often be the case. I see clearly indeed that it is not enough to extricate myself from a present difficulty by means of this subterfuge, but it must be well considered whether there may not hereafter spring from this lie much greater inconvenience than that from which I now free myself, and as, with all my supposed cunning, the consequences cannot be so easily foreseen but that credit once lost may be much more injurious to me than any mischief which I seek to avoid at present, it should be considered whether it would not be more prudent to act herein according to a universal maxim and to make it a habit to promise nothing except with the intention of keeping it. But it is soon clear to me that such a maxim will still only be based on the fear of consequences. Now it is a wholly different thing to be truthful from duty rather than from apprehension of injurious consequences. In the first case, the very notion of the action already implies a law for me; in the second case, I must first look about elsewhere to see what results may be combined with it which would affect myself. For to deviate from the principle of duty is beyond all doubt wicked; but to be unfaithful to my maxim of prudence may often be very advantageous to me, although to abide by it is certainly safer. The shortest way, however, and an unerring one, to discover the answer to this question whether a lying promise is consistent with duty, is to ask myself, "Should I be content that my maxim (to extricate myself from difficulty by a false promise) should hold good as a universal law, for myself as well as for others? and should I be able to say to myself, "Every one may make a deceitful promise when he finds himself in a difficulty from which he cannot otherwise extricate himself?" Then I presently become aware that while I can will the lie, I can by no means will that lying should be a universal law. For with such a law there would be no promises at all, since it would be in vain to allege my intention in regard to my future actions to those who would not believe this allegation, … .  Hence my maxim, as soon as it should be made a universal law, would necessarily destroy itself.

I do not, therefore, need any far-reaching penetration to discern what I have to do in order that my will may be morally good. Inexperienced in the course of the world, incapable of being prepared for all its contingencies, I only ask myself: Can you also will that your maxim should be a universal law? If not, then it must be rejected, and that not because of a disadvantage accruing from it to myself or even to others, but because it cannot enter as a principle into a possible universal legislation, and reason extorts from me immediate respect for such legislation. I do not indeed as yet discern on what this respect is based (this the philosopher may inquire), but at least I understand this, that it is an estimation of a worth which far outweighs all worth of what is recommended by inclination, and that the necessity of acting from pure respect for the practical law is what constitutes duty, to which every other motive must give place, because it is the condition of a will being good in itself, and the worth of such a will is above everything.


5)      Kant distinguishes between categorical and hypothetical imperatives.

a)      A hypothetical imperative tells you that if you want to attain a certain goal, then you must act in a certain way.  (If you want to get into medical school, then you must study hard.  If you want people to trust you, then you ought to tell the truth. Even: If you want to get into heaven, then you must obey God’s laws. )  These imperatives only apply to a person who wants to attain that goal.  That is, they only apply to me on the hypothesis that I want to attain the goal.  If I don’t want to attain that goal, then the imperative has no force for me.

b)      A categorical imperative contains no ‘if’s.  It simply tells you to do something (or not to do something).  (Don’t steal.  Honor your parents.  Never lie.)  Kant thinks that we will agree that moral rules have this form.  They apply to everyone.  You can’t evade a moral rule by saying, “Well, I don’t happen to want ______.”  (Fill in the blank with some goal.)  A moral rule would not say, for example, “Treat others kindly, if you want them to like you.”  (This is a hypothetical imperative.)  To this rule, a person might reply, “I don’t care if people like me, as long as they fear me and do as I say.” 

c)      Kant is trying to explain how it is possible for there to be a rationally valid categorical imperative.  It’s not hard to understand how reason can tell me what to do if I want to reach a certain goal.  But how can reason tell me that I ought to act in a certain way, no matter what I want?  How can there be an imperative that applies to me regardless of my goals or purposes?  What could such an imperative say?  And why should I regard it as binding on me?


6)      Since we are looking for an imperative that applies to anyone, regardless of his or her desires and purposes, we cannot appeal to those desires and purposes.  All we have to work with is “the mere concept of a categorical imperative” – that is, a command that every rational creature is obliged to obey.  Since we cannot appeal to any particular content (desire, purpose, goal), we are left with the form – that is, with the fact that this command we are looking for has the form of a law for all rational beings (Kant says “the universality of a law as such”).  So the only possible categorical imperative must be an imperative that tells us to follow the rules that are fit to be universal laws (laws for everyone).  Think about it.  Kant says it like this (using ‘maxim’ for ‘rule’):

When I conceive a hypothetical imperative, in general I do not know beforehand what it will contain until I am given the condition. But when I conceive a categorical imperative, I know at once what it contains. For as the imperative contains besides the law only the necessity that the maxims shall conform to this law, while the law contains no conditions restricting it, there remains nothing but the general statement that the maxim of the action should conform to a universal law, and it is this conformity alone that the imperative properly represents as necessary.

There is therefore but one categorical imperative, namely, this: Act only on that maxim whereby you can at the same time will that it should become a universal law.

… Since the universality of the law according to which effects are produced constitutes what is properly called nature in the most general sense (as to form), that is the existence of things so far as it is determined by general laws, the imperative of duty may be expressed thus: Act as if the maxim of your action were to become by your will a universal law of nature.



7)      In essence, then, the Categorical Imperative is a test for the rightness or wrongness of actions.  If I am thinking about acting in a certain way, I should ask myself whether I can reasonably want everyone to act in that way.  More precisely, I should ask myself, “What rule would I be following, if I did what I am thinking about doing.”  My rule would include not only what I am proposing to do but also some description of the circumstances in which I am tempted to do it.  The rule, then, would look something like this: “When I am in such-and-such circumstances, I will do such-and-such.”  For example, it might be, “When I want something very badly, and I can’t afford to buy it, and I think I can steal it without getting caught, then I will steal it.”  Or it might be, “When I want something very badly, and I can’t afford to buy it, I will work and save my money until I can afford to buy it.”  Then I should ask myself whether I can reasonably want (Kant says “will”) everyone to follow this rule.  If the answer is ‘yes’, then what I am thinking of doing is morally permissible.  If the answer is ‘no’, then what I am thinking about doing is wrong. (Which of the two rules I just gave as examples would pass this test?  Why?) Try to understand the reasoning that Kant uses to show, in each of the four examples below, that what the person is proposing to do is contrary to the categorical imperative (i.e., cannot be made into a universal law).  (Examples 2 and 4 are easier to understand.  Don’t worry if #s 1 and 3 seem obscure.)  Kant's examples:


1. A man reduced to despair by a series of misfortunes feels wearied of life, but is still so far in possession of his reason that he can ask himself whether it would not be contrary to his duty to himself to take his own life. Now he inquires whether the maxim of his action could become a universal law of nature. His maxim is: "From self-love I adopt it as a principle to shorten my life when its longer duration is likely to bring more evil than satisfaction." It is asked then simply whether this principle founded on self-love can become a universal law of nature. Now we see at once that a system of nature of which it should be a law to destroy life by means of the very feeling whose special nature it is to impel to the improvement of life would contradict itself and, therefore, could not exist as a system of nature; hence that maxim cannot possibly exist as a universal law of nature and, consequently, would be wholly inconsistent with the supreme principle of all duty.

2. Another finds himself forced by necessity to borrow money. He knows that he will not be able to repay it, but sees also that nothing will be lent to him unless he promises stoutly to repay it in a definite time. He desires to make this promise, but he has still so much conscience as to ask himself: "Is it not unlawful and inconsistent with duty to get out of a difficulty in this way?" Suppose however that he resolves to do so: then the maxim of his action would be expressed thus: "When I think myself in want of money, I will borrow money and promise to repay it, although I know that I never can do so." Now this principle of self-love or of one's own advantage may perhaps be consistent with my whole future welfare; but the question now is, "Is it right?" I change then the suggestion of self-love into a universal law, and state the question thus: "How would it be if my maxim were a universal law?" Then I see at once that it could never hold as a universal law of nature, but would necessarily contradict itself. For supposing it to be a universal law that everyone when he thinks himself in a difficulty should be able to promise whatever he pleases, with the purpose of not keeping his promise, the promise itself would become impossible, as well as the end that one might have in view in it, since no one would consider that anything was promised to him, but would ridicule all such statements as vain pretences.

3. A third finds in himself a talent which with the help of some culture might make him a useful man in many respects. But he finds himself in comfortable circumstances and prefers to indulge in pleasure rather than to take pains in enlarging and improving his happy natural capacities. He asks, however, whether his maxim of neglect of his natural gifts, besides agreeing with his inclination to indulgence, agrees also with what is called duty. He sees then that a system of nature could indeed subsist with such a universal law although men (like the South Sea islanders) should let their talents rest and resolve to devote their lives merely to idleness, amusement, and propagation of their species- in a word, to enjoyment; but he cannot possibly will that this should be a universal law of nature, or be implanted in us as such by a natural instinct. For, as a rational being, he necessarily wills that his faculties be developed, since they serve him and have been given him, for all sorts of possible purposes.

4. A fourth, who is in prosperity, while he sees that others have to contend with great wretchedness and that he could help them, thinks: "What concern is it of mine? Let everyone be as happy as Heaven pleases, or as he can make himself; I will take nothing from him nor even envy him, only I do not wish to contribute anything to his welfare or to his assistance in distress!" Now no doubt if such a mode of thinking were a universal law, the human race might very well subsist and doubtless even better than in a state in which everyone talks of sympathy and good-will, or even takes care occasionally to put it into practice, but, on the other side, also cheats when he can, betrays the rights of men, or otherwise violates them. But although it is possible that a universal law of nature might exist in accordance with that maxim, it is impossible to will that such a principle should have the universal validity of a law of nature. For a will which resolved this would contradict itself, inasmuch as many cases might occur in which one would have need of the love and sympathy of others, and in which, by such a law of nature, sprung from his own will, he would deprive himself of all hope of the aid he desires.


8)      Kant now introduces another important (and famous) idea. He claims that the categorical imperative can be expressed in a different way: as a principle requiring us to respect persons  (to treat them as ‘ends in themselves’ and not just as means to your ends).  He thinks that this new ideas is (in some sense) equivalent to the earlier ones.  This is not easy to see.

a)       Try to get clear on Kant's distinction between an objective end and a subjective (or contingent) end.  ("End" here means, roughly, "goal," "purpose," or "reason for acting.") 

b)      Note his claim that only an objective end can give us a moral law.  I think the idea is roughly this: Because it is a categorical imperative, the moral law commands us to act in certain ways regardless of what we want or how we feel.  This makes sense only if there are some creatures in the world whose value we must respect regardless of what we want or how we feel about them.  Such creatures are those we call persons.  Persons must be respected even when they are thwarting our plans and even when we don’t like them.   (It is important to keep in mind, though, that the respect Kant is talking about here is not the sort of respect we feel for people who are especially accomplished or noble.  It might be called ‘minimal respect’ – the sort of respect a person deserves just because he or she is a person.  One can respect a person, in this sense, even while punishing them for committing a crime.)  If there were no such creatures, if everything in the world had only instrumental value (like a tool), then there would be nothing wrong with doing whatever you wanted.  We wouldn’t need morality; there would be no moral law. Kant puts it like this:


The will is conceived as a faculty of determining oneself to action in accordance with the conception of certain laws. And such a faculty can be found only in rational beings. Now that which serves the will as the objective ground of its self-determination is the end, and, if this is assigned by reason alone, it must hold for all rational beings. On the other hand, that which merely contains the ground of possibility of the action of which the effect is the end, this is called the means. The subjective ground of the desire is the incentive, the objective ground of the volition is the motive; hence the distinction between subjective ends which rest on incentives, and objective ends which depend on motives valid for every rational being. Practical principles are formal when they abstract from all subjective ends; they are material when they assume these, and therefore particular incentives to action. The ends which a rational being proposes to himself at pleasure as effects of his actions (material ends) are all only relative, for it is only their relation to the particular desires of the subject that gives them their worth, which therefore cannot furnish principles universal and necessary for all rational beings and for every volition, that is to say practical laws. Hence all these relative ends can give rise only to hypothetical imperatives.

Supposing, however, that there were something whose existence has in itself an absolute worth, something which, being an end in itself, could be a source of definite laws; then in this and this alone would lie the source of a possible categorical imperative, i.e., a practical law.

Now I say: man and generally any rational being exists as an end in himself, not merely as a means to be arbitrarily used by this or that will, but in all his actions, whether they concern himself or other rational beings, must be always regarded at the same time as an end. All objects of the inclinations have only a conditional worth, for if the inclinations and the wants founded on them did not exist, then their object would be without value. But the inclinations, themselves being sources of want, are so far from having an absolute worth for which they should be desired that on the contrary it must be the universal wish of every rational being to be wholly free from them. Thus the worth of any object which is to be acquired by our action is always conditional. Beings whose existence depends not on our will but on nature's, have nevertheless, if they are irrational beings, only a relative value as means, and are therefore called things; rational beings, on the contrary, are called persons, because their very nature points them out as ends in themselves, that is as something which must not be used merely as means, and so far therefore restricts freedom of action (and is an object of respect). These, therefore, are not merely subjective ends whose existence has a worth for us as an effect of our action, but objective ends, that is, things whose existence is an end in itself; an end moreover for which no other can be substituted, which they should subserve merely as means, for otherwise nothing whatever would possess absolute worth; but if all worth were conditioned and therefore contingent, then there would be no supreme practical principle of reason whatever.

If then there is a supreme practical principle or, in respect of the human will, a categorical imperative, it must be one which, being drawn from the conception of that which is necessarily an end for everyone because it is an end in itself, constitutes an objective principle of will, and can therefore serve as a universal practical law. The foundation of this principle is: rational nature exists as an end in itself. Man necessarily conceives his own existence as being so; so far then this is a subjective principle of human actions. But every other rational being regards its existence similarly, just on the same rational principle that holds for me: so that it is at the same time an objective principle, from which as a supreme practical law all laws of the will must be capable of being deduced. Accordingly the practical imperative will be as follows: So act as to treat humanity, whether in your own person or in that of any other, never simply as a means, but always at the same time as an end.


c)      Now he discusses the same four examples from this new angle.  Do some of them make more sense when considered in this new way than they did when they were discussed in terms of ‘universal law’? He says:


To abide by the previous examples:

Firstly, under the head of necessary duty to oneself: He who contemplates suicide should ask himself whether his action can be consistent with the idea of humanity as an end in itself. If he destroys himself in order to escape from painful circumstances, he uses a person [himself] merely as a mean to maintain a tolerable condition up to the end of life. But a man is not a thing, that is to say, something which can be used merely as means, but must in all his actions be always considered as an end in himself. I cannot, therefore, dispose in any way of a man in my own person so as to mutilate him, to damage or kill him. (It belongs to ethics proper to define this principle more precisely, so as to avoid all misunderstanding, e. g., as to the amputation of the limbs in order to preserve myself, as to exposing my life to danger with a view to preserve it, etc. This question is therefore omitted here.)

Secondly, as regards necessary duties, or those of strict obligation, towards others: He who is thinking of making a lying promise to others will see at once that he would be using another man merely as a mean, without the latter containing at the same time the end in himself. For he whom I propose by such a promise to use for my own purposes cannot possibly assent to my mode of acting towards him and, therefore, cannot himself contain the end of this action. This violation of the principle of humanity in other men is more obvious if we take in examples of attacks on the freedom and property of others. For then it is clear that he who transgresses the rights of men intends to use the person of others merely as a means, without considering that as rational beings they ought always to be esteemed also as ends, that is, as beings who must be capable of containing in themselves the end of the very same action.*

Thirdly, as regards contingent (meritorious) duties to oneself: It is not enough that the action does not violate humanity in our own person as an end in itself, it must also harmonize with it. Now there are in humanity capacities of greater perfection, which belong to the end that nature has in view in regard to humanity in ourselves as the subject: to neglect these might perhaps be consistent with the maintenance of humanity as an end in itself, but not with the advancement of this end.

Fourthly, as regards meritorious duties towards others: The natural end which all men have is their own happiness. Now humanity might indeed subsist, although no one should contribute anything to the happiness of others, provided he did not intentionally withdraw anything from it; but after all this would only harmonize negatively not positively with humanity as an end in itself, if every one does not also endeavour, as far as in him lies, to forward the ends of others. For the ends of any subject which is an end in himself ought as far as possible to be my ends also, if that conception is to have its full effect with me.


9.   In a footnote Kant criticizes a version of the Golden Rule:

*Let it not be thought that the common "quod tibi non vis fieri, etc." [Do not do to others what you would not want done to you.]  could serve here as the rule or principle. For it is only a deduction from the former, though with several limitations; it cannot be a universal law, for it does not contain the principle of duties to oneself, nor of the duties of benevolence to others (for many a one would gladly consent that others should not benefit him, provided only that he might be excused from showing benevolence to them), nor finally that of duties of strict obligation to one another, for on this principle the criminal might argue against the judge who punishes him, and so on.

Why does Kant say that a criminal could use the Golden Rule to argue against a judge who was punishing him? I think it goes like this: If I am a judge I must give criminals what they deserve, not what they want (or what I would want if I were in their shoes).  This seems to violate the Golden Rule.  But it doesn’t violate Kant’s principle, because I can consistently will that everyone follow the rule: “Give criminals the punishment they deserve.”  It’s true that willing this rule is willing my own punishment, if I commit a crime.  But I don’t have to commit a crime.  So my desire to avoid punishment is not in conflict with my intention to punish criminals.  This case is different from a case where I might be considering whether or not it is OK to commit a crime.  If I say that it is OK for me to steal, then, by Kant’s rule, I must also be willing to say that it is OK for everyone to steal.  This includes stealing from me.  So, by willing that everyone follow the rule, “Steal, when you think it’s the best way to get what you want,” I am willing that others steal from me when it is to their benefit.  And I cannot control whether or not they will be in a position to take advantage of me in this way, or not.  (I have some control, in that I can take precautions.  But, as a vulnerable and fallible human being, I cannot rationally suppose that I could never be victimized.)  So, when I ‘will that this maxim become a universal law’, my will is in conflict with my desire not to be robbed.   Since crime victims do not normally ‘volunteer’ to be victimized, they are not in the same position as a criminal who is about to be punished.  The criminal is a ‘volunteer’.  He has chosen to commit a crime.  So Kant’s principle has this welcome result:  It helps us see why it is right to punish criminals and wrong to steal from innocent victims, even though in both cases we are doing to others what we would not want done to us.  The Golden Rule can lead to confusion on this point.