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Traditionally, utilitarians were hedonists, believing that utility consists in pleasurable mental states. So e.g. Jeremy Bentham thought that the right thing to do was to produce the most pleasure for all affected.
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<p>That is a strawman; Bentham did distinguish among different forms of pleasure. For example, he took into account 'fecundity' which is relevant to how extrinsic benefits can be attributed to the rightness of an action.</p>
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However, one problem with this view is it implies that what you don't know can't hurt you. For example, suppose someone secretly spread rumors behind a person's back and thereby destroys her reputation. But further suppose that she never finds out about this and experiences no ill effects from it. In this case, since she never experiences any displeasure from the act, the act doesn't harm her, according to the hedonist. This is often called "the experience requirement"; hedonism requires that the subject experience something in order for that thing to be good (or bad) for them.
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<p>That is not the case; Bentham would argue that the extrinsic benefits/utility of having knowledge is more than the combined intrinsic/extrinsic benefits/utility of apathy; for example, the former enables one to provide wise advise, or to construct inventions that could benefit the human race. Taking these considerations into account, utilitarianism is not as flawed as perceived.</p>
<p>There is a general tendency to conflate Utilitarianism with hedonism, but that line of thinking is dangerous and it does not do utilitarianism justice...
...not that there is justice to utilitarianism, but we must all give it a fair chance if we are to engender fruitful discourse... right?</p>
<p>Edit: Let me make clear that your objection does apply to strict hedonism; however, it does not apply to any form of utilitarianism, not even Bentham's.</p>
<p>Peter Singer is a radical, and he will always remain so; many scholars are apt to cast his beliefs in the 'nonsense bin', but he does make coherent propositions. I know numerous professors who believe in the permissibility of humans marrying non-humans, and they like to introduce themselves as utilitarians. That they advocate these beliefs does not imply they themselves perform them in actuality. They are merely endorsing an ethical framework, and within that framework, they are supposing that some actions are right while others are not.</p>
<p>I could opine an ethical framework which rendered permissible the forced enslavement of an alien race; that my framework allows it does not imply that tomorrow I will enslave aliens.</p>