But there are also rationalist deontologies – articulated most importantly in the modern era by Immanuel Kant. Kant is famous for the Categorical Imperative (CI). In contrast with a rule- book ethics, the CI marks out a procedural way of determining what actions are right. The first formulation of the Categorical Imperative states: “So act that the maxim of your will could always hold at the same time as a principle establishing universal law”. One of Kant’s own examples from the Foundations of the Metaphysics of Morals helpfully illustrates what this means. Consider the possibility of needing to borrow money – knowing full well, however, that you will not be able to repay the loan. You also know that, in order to get the loan, you have to promise to repay it (duh). Question: can you make what you know to be a false promise in order to secure the loan? For Kant, the maxim of this action would be: “When I believe myself to be in need of money, I will borrow money and promise to repay it, although I know I shall never do so.” But the Categorical Imperative requires that we ask: “How would it be if my maxim became a universal law?”
This might well remind you of your parents asking you in high school: what if everyone did that? But, for Kant, what is at stake in this question is whether or not the larger social order that would result from everyone following the maxim of “make a false promise when it is convenient to do so” would be coherent – or logically contradictory. On Kant’s analysis, attempting to universalize this maxim would become self-contradictory:
For the universality of a law which says that anyone who believes himself to be in need could promise what he pleased with the intention of not fulfilling it would make the promise itself and the end to be accomplished by it impossible; no one would believe what was promised to him but would only laugh at any such assertion as vain pretense.