Are ethical hedonists right? Is happiness the only important thing about life; the thing we should be exclusively interested in maximizing?

Robert Nozick presented an interesting thought-experiment in The Examined Life (and also discussed this in Anarchy, State, and Utopia):

Imagine a machine that could give you any experience (or sequence of experiences) you might desire. When connected to this experience
machine, you can have the experience of writing a great poem or bringing about world peace or loving someone and being loved in return. You can experience the felt pleasures of these things, how they feel “from the inside.” You can program your experiences for tomorrow, or this week, or this year, or even for the rest of your life. If your imagination is impoverished, you can use the library of suggestions extracted from biographies and enhanced by novelists and psychologists. You can live your fondest dreams “from the inside.”

Would you choose to do this for the rest of your life? If not, why not? (Other people also have the same option of using these machines which, let us suppose, are provided by friendly and trustworthy beings from another galaxy, so you need not refuse connecting in order to help others.) The question is not whether to try the machine temporarily, but whether to enter it for the rest of your life. Upon entering, you will not remember having done this; so no pleasures will get ruined by realizing that they are machine-produced. Uncertainty too might be programmed by using the machine’s optional random device (upon which various preselected alternatives can depend).

Would you connect for the rest of your life?

Please ignore any issues you may have about whether such a machine is possible (assume that it is). The point is to test whether you really believe that all that matters, ultimately, is your internal feeling of happiness.

I think most people would not permanently connect to such a machine, and they’d be correct to make that choice. Happiness is good because it is a signal that things are going well; that our values are being furthered. But, what’s important are the things, not the signal. Focusing exclusively on happiness is like focusing on the symptom rather than the disease.

For most of us, our values involve real things in the real world. This connection with reality is very important to us; it gives our lives meaning. Responding to a simulation, while useful for providing fun and knowledge, is not what we most want.

I think Nozick sums up very well:

We want experiences, fitting ones, of profound connection with others, of deep understanding of natural phenomena, of love, of being profoundly moved by music or tragedy, or doing something new and innovative, experiences very different from the bounce and rosiness of happy moments. What we want, in short, is a life and a self that happiness is a fitting response to—and then to give it that response.