Utilitarianism tends to retain whatever appeal it has by an illicit back-and-forth between two quite different positions, a corporeal hedonism on the one hand and a more evanescent ethical satisfactionism on the other. As Nozick emphasized with his hypothetical "experience machine," we value more in life than pleasure. We value more in life than any set of internal states of our own body/mind, states that could be produced by a machine. We value doing and achieving X, not just the illusion that we did it and achieved it. Heck, this is the moral of the Matrix movies. Even beyond the Cartesian stuff, the point is that if the machines that had taken over the world and confined all humans in tubes were nice enough to give all those humans the most pleasant fantasies, the situation would still be an oppressive one whence revolutionaries would rightly seek to free us. So we naturally make the move away from hedonism or any hedonistic reading of utilitarianism...