I'm not sure that most contemporary Kantian moral philosophers agree with Kant on the morality of prostitution. As you note, prostitution does not seem to make use of one's own humanity in a way that's fundamentally different from other forms of work or labor which are clearly morally permissible. Why think that prostitution, unlike farming, involves the wrongful use of ourselves merely as a means? Much of the reason is that Kant was deeply skeptical about the compatibility of sexual desire with the moral requirement to treat rational agents as ends in themselves rather than merely as a means. He writes: “Sexual union is the reciprocal use that one human beings makes of the sexual organs and capacities of another” for the purpose of enjoyment. As Kant saw it, sexual desire is not a desire for a person's good but for the use of their body for one's own physical pleasure. Hence, sexual desire is fundamentally at odds with respect for others' rational natures. Sex is animalistic in that we treat ourselves ...

Unfortunately, this is a tricky question for Kantian ethics to address. On its face, it might appear that procreation (bringing a child into existence) in order to advance one’s own happiness treats the child merely as a means: One ‘uses’ the child to promote one’s own happiness. But things get more complicated once we attend to exactly what this Kantian imperative says. The Kantian moral requirement you mention states that we are not to treat “humanity” merely as a means. There are debates as to exactly what Kant had in mind by “humanity” but the standard view is that “humanity” means the capacity for rational agency — the ability to choose our ‘ends’ (our goals or objectives) and the best means to those ends. But a newborn lacks “humanity” in this sense; it cannot choose ends for itself, etc. Nor can a fetus. All the more, a child who does not yet exist does not have humanity! Hence, it would appear that the apparent answer to your question is ‘no’: You cannot treat someone’s capacity for...

Thanks for your question. Before my response, a brief observation: You speak of principles being "maximized". I suspect you're confusing Kant's notion of a maxim with some other idea from moral philosophy (perhaps the utilitarian claim that right actions are those that maximize well-being). A maxim, for Kant, is a justifying principle of action with the form "I will do act A in circumstances C to achieve end E". Kant's Formula of Universal Law requires that we act only on maxims that can be consistently universalized. There's a lot of controversy as to precisely what it means for a maxim to be consistently universalizable. Here's a description, provided by Robert Johnson in his Stanford Encyclopedia of Philosophy article on Kant's moral philosophy, of the procedure to be used to evaluate whether a maxim can be consistently universalized: First, formulate a maxim that enshrines your reason for acting as you propose. Second, recast that maxim as a universal law of nature governing all rational agents,...

Second question first: Of course not! If 'talking back' means picking arguments with a teacher, that's not very productive -- or very philosophically minded. That said, I think many philosophers would agree that too much of formal education emphasizes the memorization or assimilation of 'established' knowledge as the expense of the sort of curiosity and questioning found in philosophy. There's a worldwide movement to promote philosophy education for children. Here are some good resources on that front: http://depts.washington.edu/nwcenter/ http://p4c.com/ As to your first question: I don't have any empirical data to support this -- to my knowledge, how philosophers raise their children has never been studied. All the same , I would not at all be surprised to learn that many of the traits that one needs to be successful in philosophy -- a sense of puzzlement, attention to reasoning, comfort with uncertainty, respect for those with whom one disagrees -- are passed on by philosophers to their children. I...

Philosophy is a highly discursive discipline founded on argumentative give and take. Often when a philosopher's position is subject to criticism she believes she cannot answer, she modifies her position while trying to retain those elements of those position she believes are most central to it. In other words, the result of receiving criticism is rarely a philosopher 'admitting defeat.' Rather, her position evolves as she strives to absorb the criticisms as much as her extant positions allow. That said, there are some prominent examples of philosophers who clearly changed their minds over their lifetimes. Perhaps the clearest is Wittgenstein: The 'early Wittgenstein' inspired logical positivism, the 'later' ordinary language Wittgenstein was a critic of positivism. Russell seemed to change his mind a fair bit too. A recent example is John Rawls, who gives a very different foundation for his political liberalism in his early work than in his later work. Kant certainly changed his mind regarding whether...