 One example of an argument with this structure is as follows. First it is noted that “S morally ought to φ” is true only if S is a moral agent. The further conceptual steps of the argument then seek to establish that in order to be moral agent, S must have the capacity to perform actions that are morally blameworthy and praiseworthy, and that these capacities presuppose that S has a certain kind of control over their actions. The ontological step of the argument then seeks to establish that no such autonomous control exists in nature; it’s an illusion. (See entry for  skepticism about moral responsibility.)  A couple of iterations of modus tollens then take us to the conclusion that “S morally ought to φ” is never true.