People often read Kant as giving a principle of pure reason from which rational laws of pure practical reason can be deduced. From the moral imperative (which is categorical, not hypothetical, because it applies to people no matter the situation) which has three formulations, we certainly must be able to deduce determinate moral content. The question is whether any determinations about actions in a situation can be known beforehand, without completely cognizing the particularities of that situation.
There are three formulations of the moral law in Kant. The first is, act such that the maxims (subjective principles) on which your will is grounded in an action could be made a principle for universal lawmaking. This is the most common formulation of the “categorical imperative” (most Kantians simply call this “the moral law” because it is not as if sometimes you obey a categorical imperative and sometimes a hypothetical one, rather to be moral you must always obey the catagorical imperative, that’s why its called “categorical”, even though every situation you actually encounter has hypothetical considerations – a “for the sake of which” element).
Can determinate moral laws be deduced from this? Let us look at an example. In Theorem 3, remark, Kant puts a possible maxim to the test: “to increase my wealth by every safe means”. The situation he refers to considers appropriating a bank deposit belonging to someone else, knowing that one will not be found out. However, he finds in it a contradiction because if this principle was used to ground a universal law, “there would be no deposits at all”, i.e., there would be no banks if people stole form them at every safe opportunity.
Thus, it looks like we have a principle of universal lawgiving: do not appropriate your wealth by any safe means. But this does not say very much at all – just that some attempted universal law was a failure, but nothing meaningful follows from this. It is no more meaningful than to try out a new theory of how to make pots, and it turns out to make bad pots, so you deduce the maxim: do not make pots in this bad way. Fine, you could say it, no one would pay any attention – moral content will come from laws that prescribe action, not which prescribe not taking up a law which would prescribe action.
So, you might say, the universal principle is “don’t steal”, but this isn’t in the text. You can check, the example appears on page 25 of the Cambridge edition of the Critique of Practical reason, and as far as I know the example appears no where else in Kant. It would likely turn out if you tried to universalize the maxim “don’t steal” that it giving it the principle of universal law would destroy it. I can’t say, I’m not an expert moral philosopher, but the fact Kant doesn’t make this jump is enough to make us at least worried about it.
Also, Kant says on the previous page, “It would be better to maintain that there are no practical laws at all but only counsels on behalf of our desires tan to raise merely subjective principles to the rank of practical laws, which absolutely must have objective and not merely subjective necessity, and which must be cognized a priori by reason, not by experience (however empirically universal this may be).”(24)
I’m not going to talk today about the other two formulations of the moral law (act such that you treat others as ends and never as means, and act as if you were a legislator in the kingdom of ends). The second one is confusing because it means treat other people as the kinds of beings that have themselves as their own end, not treat others always as ends of your actions rather than means to your ends.
There is, however, another secret formulation in the second critique that is often overlooked, and it is the secret to thinking Kant’s notion of freedom as obeying a non empirical law. The statement is this:
“ask yourself whether, if the action you propose were to take place by a law of the nature of which you were yourself a part, you could indeed regard it as possible through your will.”(60)
The idea is to imagine that you live in a world where you are radically unfree, and you are cognizant of this (not the pseudo unfreedom of scientism, the strong unfreedom of science fiction distopia). Now you will perform many actions, many of which are ones which you could not affirm, that strongly conflict with your will. However, some actions will be such that you could say, “I might have done that”, so you can affirm them as the kind of thing you may have willed if you had been given a free will. Free actions, Kant believes, are those ones – the ones that you can affirm as manifestations of your freedom, but which follow from a law. (The question of ‘what is the law’ is not a problem for Kant – he’s given three determinations of it.)