Philosopher Robert Nozick poses this question. Suppose you could attach your body for the remainder of your life to an "experience" machine. Floating in a tank of fluid, connected by electrodes to an incredibly advanced computer, you would spend the rest of your days fully realizing your greatest personal dreams.
You could win the Pulitzer Prize, the Super Bowl, the Indy 500, invent a cure for cancer, travel in outer space. Any dream you wish comes true. These experiences would not be true in reality, but they would be utterly indistinguishable to you from reality.
Given this choice, would you plug yourself in, thus ensuring the perpetual satisfaction of all your most cherished desires?
For those who opt out, see the post below for what makes most people happy, at least in America.