Robert Nozick, answered from the texts and cited to the page.
Imagine a machine that could give you any experience you desired — the feeling of writing a great novel, of being loved, of achieving deep friendship — while you floated in a tank with electrodes.1 You would have all and only the experiences you wanted, indistinguishable from real life, with no awareness that you were in the tank. Should you plug in for the rest of your life?
Most people, asked, refuse. The refusal shows that we want not merely to have certain experiences but to do certain things, to be certain kinds of persons, to be in genuine contact with reality rather than with a constructed simulation. We care about the world being a certain way, not just about our impressions being a certain way. This refutes hedonism in any form that takes pleasurable experience as the sole intrinsic good.
Pleasure is a good, but it is not the only good; doing, being, and connecting are goods that hedonism cannot accommodate.2345
THE EXPERIENCE MACHINE There are also substantial puzzles when we ask what matters other than how people's experiences feel "from the inside." Suppose there were an experience machine that would give you any experience you desired. Superduper neuropsychologists could stimulate your brain so that you would think and feel you were writing a great novel, or making a friend, or reading an interesting book.Anarchy, State, and Utopia, p. 42
Someone enjoys an activity to the extent he engages in the activity because of its own intrinsic properties, not simply because of what it leads to or produces later. Its intrinsic properties are not limited to felt qualities, though; this leaves open the possibility that something is enjoyed yet not pleasurable.The Examined Life, pp. 104–105
If you are worried about missing out on desirable experiences, we can suppose that business enterprises have researched thoroughly the lives of many others. You can pick and choose from their large library or smorgasbord of such experiences, selecting your life's experiences for, say, the next two years.Anarchy, State, and Utopia, p. 43
Readers who hold they would plug in to the machine should notice whether their first impulse was nor to do so, followed later by the thought that since only experiences could matter, the machine would be all right after all. Few of us really think that only a person's experiences matter.The Examined Life, p. 106
And they'd all be wrong. Anyone making a similar inference shouldn't have much confidence in it. Perhaps a better inference procedure would be to assume that everything that behaved like you and had the same functional and physical states as yourself was also like you in internal mental life as well.Socratic Puzzles, pp. 335–336
Among the most famous and most reproduced thought experiments in late-twentieth-century philosophy. The argument has been taken as decisive against hedonism in mainstream well-being theory; recent empirical work (De Brigard) has questioned whether the experience-machine intuition reflects genuine moral judgment or merely status-quo bias. Contemporary hedonists offer revised versions of the doctrine that accommodate the intuition (preference hedonism, attitudinal hedonism) without conceding the underlying point.