If what makes something immoral is any act that harms someone, would deliberately harming oneself count as an immoral act? And if some other person who is harmed agreed to be harmed, would that be immoral?

Excellent and highly relevant to some contemporary debates. A very minor first point, something might be immoral (for example, kicking dogs) even if dogs are not persons (though I admit that I think of my dog Pip as a "someone). Those in what is traditionally described as liberal political theory (e.g. John Stuart Mill) give more latitude for self-harm than what is traditionally thought of as conservative (e.g. Edmund Burke). When liberals seek to interfere with persons involved with self-harm (those who seek to commit suicide or engage in high risk acts), they sometimes appeal the ways in which the self-harm might be motivated by mental illness or some other impairment (e.g. Johny does not *really* want to harm himself, he just wants attention). I suggest that many of the reasons why we think we should not harm others, applies to our own case. I should not lie to others, for example, and, similarly, I should also not lie to myself (except under outrageous conditions). Your second question goes right to the heart about debating the status of boxing and football. My colleague, who is a panelist, Gordon Marino, is a great supporter of both. I am more hesitant and I worry that the celebration of such mutual harming ("controlled violence" is a term that comes to mind) can attract young persons to being at risk for irreversible brain damage. So, my vote is that boxing and football become less grave to the effect that they are voluntary activities, but I think that the long term, deep damage done gives us reason to not culturally celebrate such practices.

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