Abstract

I consider Kant’s use of claims about “nature’s ends” in his arguments to establish maxims of homosexual sex, masturbation, and bestiality as constituting “unnatural” sexual vices, which are contrary to one’s duties to oneself as an animal and moral being. I argue, first, that the formula of humanity is the principle best suited for understanding duties to oneself as an animal and moral being; and second, that although natural teleology is relevant to some degree in specifying these duties, it cannot play a sufficiently robust role to establish Kant’s conclusion. I also discuss what the formula of humanity (along with warranted attention to natural teleology) suggests about the morality of homosexual sex, masturbation, and bestiality.