Hume thought reason was a slave to the passions. It can tell you how to achieve a certain aim, producing a principle of the form, "In order to achieve O, do A." But unless you desire or value O, such a principle (what Kant calls a "hypothetical imperative") has no force for you. Kant did not deny that reason can and does operate as a slave to the passions in this way. What he denied was that this was the only thing it could do in the domain of action. Contrary to Hume, Kant thought reason not only can but does impose a requirement on all rational beings that applies regardless of their contingent "inclinations"--a requirement that he called "the Categorical Imperative."
He thought this Categorical Imperative could be formulated in different ways. The first "formulation" runs as follows:
Act only according to that maxim which you can at the same time (consistently) will to be a universal law (of nature).
In the present post, I want to consider what this principle is saying and why Kant thinks that reason requires us to be obedient to it. In the case of the first formulation (or what I'll refer to for short as the 1st CI), these two tasks are most easily pursued together. That is, one really comes to understand what the principle is saying by thinking about what reason (as Kant understood it) demands.
Now let me pause here to say that Kant is a difficult thinker, and not everyone interprets him in precisely the same way. What I am about to provide is my understanding of the 1st CI. It's not a wildly novel or original understanding--I dare say it falls very much into the mainstream of Kant interpretation. But it is, nevertheless, my understanding and my way of formulating this understanding. Other philosophers may disagree with some of the details, or may prefer a different way of explicating things.
In terms of making sense of what Kant is saying in the 1st CI, it sometimes helps to begin with a rough picture before getting more focused--and there is no better place to start than with a little anecdote involving philosopher Sidney Morgenbesser. According to the story, Morgenbesser was leaving the New York subway, an unlit pipe in his mouth, when a police officer informed him there was no smoking on the subway. Morgenbesser pointed out he hadn't yet lit the pipe and was leaving the subway station. After a bit of back-and-forth, the officer said, "If I let you do it, I'd have to let everyone do it"--to which Morgenbesser replied with something along the following lines: "Who do you think you are? Kant?"
He was promptly arrested.
I'm assured he was eventually able to convince the authorities that he was likening the officer to the great 18th Century German enlightenment philosopher, not resorting to a vulgar insult. But the likeness here is apt. The officer was implicitly invoking something like the 1st CI, which asks us to consider the following question: "What if everyone did that?" Or, perhaps better: "What if everyone did that as a rule?"
In very loose but pedagogically helpful terms, the 1st CI is telling us that it is only legitimate for us to act in a certain way if everyone acting in that way as a rule is something we could consistently will. In other words, what we're doing has to be universalizable. But while pedagogically helpful for the sake of getting us to see what the 1st CI calls for, this way of describing the principle isn't precise enough for us to be able to clearly see why Kant thought that reason, by itself, demands obedience to it.
For that purpose, we should probably focus in on the notion of a maxim. What Kant believes must be universalizable is not our action but the maxim of the action. By a “maxim,” Kant means a subjective principle of action.
Here is the first place at which Kant's understanding of what it means to be rational is expressed within the 1st CI. Kant thought that reason is, by its nature, an abstractive faculty: it abstracts from the particular level to the general or universal level. It uncovers patterns, regularities, laws. In the domain of action, this means that to be rational is to behave in a rule-governed way, to act in accord with a rule.
Now, of course, we’re not always intending to follow a rule when we do something. But even then, we can ask ourselves, “What rule would I be following in this case were I conforming my action to a rule?” The answer to that question is the maxim of the act, the principle that your act falls under The maxim of your act is the principle you’d be following were you deliberately seeking to behave in a rule-governed way.
Of course, there are difficulties here, because there are numerous ways to generalize, various degrees of generality, and hence a number of rules that any particular action might conform to. Put more simply, the very same act in the very same circumstances might be called for by a number of different rules. So which one is your maxim?
In fact, much of the difficulty in interpreting Kant turns on this very issue. One neo-Kantian, R.M. Hare, argued that the proper "maxim" for your action is arrived at by removing from the description of your act all particular or individual references while preserving maximal specificity--such that the maxim says, in effect, "Do actions like this (specified in exhaustive detail) under conditions like these (specified exhaustively)." But few think that this is what Kant had in mind, and most neo-Kantians don't follow Hare's lead here.
Despite the importance of this controversy, I won't pursue it here. My aim here is to understand why Kant thought reason required obedience to the 1st CI; and I think we can begin to get a handle on that even if many important problems remain to be solved.
In any event, Kant thought that being rational in one's actions required operating in a rule-governed way, which means following a maxim. But the demands of rationality do not end there, because Kant didn’t think any old maxim is necessarily going to be rational. While operating in a rule-governed way is a condition for rationality, it is not the only condition. One's rule of action has to be a rational rule. And there are certain conditions a rule has to meet in order to be a rational rule. The 1st CI is, in effect, an effort to articulate these conditions. To be rational, you need to act in accord with a rule that passes the test specified in the 1st CI: Can one preserve consistency in one's will if one wills that one's maxim be universalized?
In a nutshell, Kant is supposing that rationality requires consistency of will (to will inconsistent things is to be irrational) and consistency across cases (in the sense that one must treat like cases alike, and hence be governed by rules that are universal in the sense of calling for the same kind of thing in all relevantly similar conditions). A maxim that can't be applied consistently across relevantly similar cases without generating an inconsistency of will is thus doomed to irrationality. To preserve consistency of will (which reason requires), you'll need to refrain from universalizing your maxim (but reason also requires that). To universalize your maxim (which reason requires), you'll need to land your will in a contradiction.
Hence, reason requires that you only act on maxims that you can universalize without generating an inconsistency in your will. This, then, is a categorical imperative of reason, one that reason generates all by itself (apart from the passions), and that is demanded by reason regardless of one's inclinations. If your maxim doesn't meet the test of the 1st CI, then reason precludes acting on it no matter how much you might want to.
But so far this is all expressed in very abstract terms--and as such, certain crucial questions are left unanswered. For example, what, exactly, is a contradiction in one's will? And how could universalizing one's maxim lead to such a contradiction? To answer these questions, it is probably most helpful to look at some concrete cases. And I can think of no better case to start with than one Kant himself makes use of himself.
In fact, Kant offered four examples of how the Categorical Imperative works in practice, but one of them is offered twice (in different sections of his Groundwork for the Metaphysics of Morals), apparently because he thought it was particularly helpful. This is the example of making a false promise. He asks us to imagine someone who desperately needs to borrow money, knows he will be unable to repay the lender, but also knows that no one will lend him the money he needs unless he makes a promise to repay within a certain time frame (a promise which, given his inability to repay, can only be a false one).
Can the making of such a false promise be morally permissible? Kant's answer, based on the 1st CI, is no. Here's how he explains it:
...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 him, but would ridicule all such statements as vain pretenses.Kant really makes two points here with respect to the attempt to universalize the "false promise maxim." First, were it universalized the institution of promising would collapse. If everyone made false promises as a matter of universal law, no one would be able to make a false promise because no one would be able to make a promise.
One way to understand this is to think of what a promise is. In terms of its grammar, a promise is a "performative"--one performs a certain kind of act by saying that one does the act. But as with other performatives, there is a social context of mutual understandings which makes it possible to perform the act in question by uttering certain words. A minister who says "I now pronounce you husband and wife" under the proper conditions is able by those words to create a social relationship because of a complex set of social agreements that have been put into place. Take away those social agreements, and the words become empty. The minister is no longer able to marry anyone by saying those words. Likewise, the practice of promising is a social institution that exists only on the condition that certain mutual understandings are in place--and those mutual understandings would not be in place in conditions C were the making of false promises under conditions C a universal law. To will that everyone live by the maxim is impossible, because if everyone lived by the maxim no one could.
And so there is a practical contradiction bound up with willing the maxim to be a universal law: You simultaneously will (a) that everyone act in a certain way and (b) that it be impossible for them to act in that way. This, for Kant, is paradigmatically irrational. But refusing to treat like cases alike--refusing to universalize your maxim--is also paradigmatically irrational. Hence, there is no way to be rational while acting on this maxim. Reason therefore rules it out. There is a categorical prohibition on making false promises, whether the making of such promises is subjectively appealing to you or not.
But few cases are quite as neat as this, where it would be impossible for anyone to act on a maxim were everyone to act on it (arguably, a prohibition on stealing could be justified in these terms since stealing by definition invokes the notion of private property, which would not exist under a universal maxim of theft). But Kant also points out a second way in which the false promise maxim generates a practical contradiction when universalized. It is not just the making of the promise that becomes impossible, but also "the end that one might have in view in it." In making a false promise in this case, one is attempting to achieve thereby a certain objective--getting the loan. But were it a universal law that people make false promises in such cases, no one would loan money on the strength of a promise of repayment. So the end or goal for which one wills the maxim in one's own case is an end or goal that could not be realized if everyone acted on that maxim.
When you will the maxim in your own case, it is for the sake of achieving an end that would be rendered impossible for you to achieve were you also to will that the maxim of your action be a universal law. To will that your maxim be universalized is therefore to will a certain action for the sake of a certain objective, and to at the same time will that conditions prevail such that it be impossible for you to achieve your objective through this course of action. But to will the achievement of O via A, and at the same time to will that it be impossible to achieve O via A, is paradigmatically irrational. It's to will contradictory things. So, in order to be rational you must universalize your maxim--but universalizing this maxim involves a practical contradiction given the end for which you are willing the maxim in your own case. So either you universalize and land yourself in a contradiction, or you avoid contradiction by refusing to universalize (by, in effect, refuse to behave in the law-like, treat-like-cases-alike way that is definitive of rationality for Kant).
This second kind of practical contradiction does not just apply to false promises and a narrow range of similar practices. It clearly applies to lying in general (which only works in a context of honesty), and it also seems to be the same basic kind of contradiction that Kant thinks arises with respect to what we might call the egoist maxim--which is a second of the four examples Kant brings up to illuminate the 1st CI.
The egoist maxim is, in a nutshell, this: Look out exclusively for your own happiness and let others look our for their own. Kant thinks that the world might continue to chug along if this maxim "should have the universal validity of a law of nature," but he doesn't think anyone could consistently will this maxim. On the contrary, "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." Put simply, if you will this maxim in your own case it is for the sake of your own happiness--but your happiness is better served in a world where following your maxim is not a universal law. This is not quite as strong a contradiction as you get when it would be impossible to achieve your end were everyone to follow your example. He's not saying that happiness is always impossible to achieve in a world where everyone just looks out for themselves--just that it's much harder to achieve, and that chances are (given the world in which we live) you'll encounter circumstances in which your happiness will depend on the good will of others.
Kant uses a pair of other examples to highlight how the 1st CI works and why he believes reason demands obedience to it--both of which are, in my experience, more controversial to dominant modern sensibilities. The first considers the suicidal maxim: take your own life when the future is likely to hold more misery than joy. The second considers what I'll call the lazy wastrel maxim: let your talents go undeveloped in favor of indulging in empty pleasures. In both cases, there is a bit more emphasis of the language of "nature"--testing whether the maxim could be willed as a law of nature, or as something "implanted in us" as a "natural instinct."
With respect to the suicidal maxim, Kant thinks that a world in which this maxim operates as a natural law "could not exist as a system of nature," because it would involve "the very feeling whose special nature it is to impel to the improvement of life" being directed in a law-like way towards the destruction of life. According to Kant, the life-improvement instinct couldn't be the life-improvement instinct if it consistently dictated self-destruction under certain conditions.
Why not, we might ask? Can't an instinct be a qualified instinct and still be a coherent and consistent one?
With respect to the lazy wastrel maxim, Kant is clear "that a system of nature could indeed subsist with a such a universal law." So he is explicitly contrasting it with the suicidal maxim. It is to the suicidal maxim, if you will, what the egoist maxim is to the lying promise maxim. What Kant argues is that while a system of nature could exist in which everyone neglects the cultivation of their talents and abilities, no rational being could will that this be a driving natural instinct that rules human behavior. Why? Because "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." At least it sounds very much as if Kant is saying that reason necessarily wills certain ends--ends which would not be served if the lazy wastrel maxim were universalized. But Kant's defense of this idea is a single sketchy sentence that has left more than one reader scratching their heads.
Some argue that these two examples implicitly invoke elements of the natural law tradition in which Kant was steeped. Some contemporary followers of Kant seem to think that, for this reason, they can simply ignore these examples, setting them aside (as somehow infected with the theoretical baggage of Kant's era) in favor of the examples that more cleanly focus on notions of rational consistency.
But this strikes me as a mistake for several reasons. First of all, Kant chose his examples quite carefully in order to elucidate different ways in which a maxim can fail the test of the 1st CI, and so there may be important lessons to be learned about the scope of the CI that emerges when we investigate these examples--lessons that may be important even if we aren't convinced by the specific examples.
Second, Kant was in the habit of attempting to reframe inherited ideas within the context of his own philosophical system--in effect exploring the possibility that traditional notions might embody an implicit wisdom that Kant's philosophical investigations could reveal. As such, it may be that Kant is trying to "vindicate" (from the standpoint of his own system of thinking) some modified version of natural law theory--showing, in effect, that traditional moral ideas can be justified by appeal to the demands of practical rationality. If so, it is worth exploring the extent to which he succeeds.
Third, Kant may have deliberately embraced important elements of the natural law tradition that preceded him because he recognized something profound and important in them that he wanted to preserve within his own moral philosophy. Perhaps those of his examples that seem to be more tied to this older tradition are so puzzling because he had not yet succeeded in integrating the insights from this older tradition into his account of how morality can be grounded in the demands of reason. But investigating Kant's (presumed) failure here may prove fruitful--perhaps even as a pathway to revising Kant's theory in beneficial ways.
That said, this post has gotten plenty long already--and there is enough room for critical discussion in relation to the examples that, in my experience, are more compelling to modern sensibilities.
In my next main post in this series, I want to turn to the Second Formulation of the Categorical Imperative--the so-called "formula of humanity" which holds that we must always treat humanity as an end and never as a means only. Here we encounter a fundamental principle which is more substantive in what it requires than is the 1st CI (which, like the Golden Rule to which it has been likened, is a more formal principle in the sense of offering a formula for determining whether something is permitted as opposed to laying down specific substantive requirements). The 2nd CI (as I will call it) is also a principle which establishes an end for the sake of which we are to act--and end which, according to Kant, is given to us by reason.