It seems to me that Kant's categorical imperative implies that we all have a
I used exactly this example in an essay published over 20 years ago as one of the arguments in support of a more subtle interpretation that had been first proposed by Tim Scanlon. On this reading, it is the permission one is claiming for oneself that is to be universalized. So instead of asking whether one can will that all people act on one's maxim of remaining childless, one is to ask instead whether one can will that all people be permitted to remain childless. In the world as it is, we can certainly will this universal permission (because enough others would decide to conceive even without a duty to do so), and therefore each of us is permitted to act on the maxim in question.