Part of the difficulty in defining moral rules stems from the fact that each individual experiences the world differently. What I perceive as pain may feel like minor discomfort to someone else. If there is common ground from which to build a set of moral rules, it seems we will have to start with something more substantial than perceived experiences. To illustrate this point, philosopher Robert Nozick imagined a so-called experience machine that would give users whatever experiences they wanted. He argued that most people would find this machine unsatisfying. We don’t just want the perception of experiences; we want to act and live out those experiences. Nozick’s experience machine shows that our physical bodies and actions are essential to the lives we want to live. And we need them in order to understand and practice morality.
Nozick conceives the experience machine in the early pages of his book Anarchy, State and Utopia as he explores different ways to think about morality. How people perceive the world, how they think about it and what they want from it matter when we try to determine what moral rules constrain human behavior. But morality seems to require more than individual preferences and desires. Somehow, morality requires that we translate individual experiences into rules that apply to everyone. Yet as Nozick observes, there are “substantial puzzles when we ask what matters other than how people’s experiences feel ‘from the inside.’” 
To explore this puzzle, Nozick describes an experience machine in which the user floats in a tank of nutrient-rich fluid with electrodes wired to her brain. Neuropsychologists stimulate her brain to give her any experience she desires. She could have the simulated experience of writing a best-selling novel, traveling to exotic destinations, completing a marathon, eating delicious food or falling in love. So, Nozick asks, “should you plug into this machine for life, preprogramming your life’s experiences?” 
His answer is no. He writes, “We want to do certain things, and not just have the experience of doing them. In the case of certain experiences, it is only because first we want to do the actions that we want the experiences of doing them or thinking we’ve done them.”  In other words, what is really important to most people is not just experiencing things, but doing them. Our experiences are enriched by physical action. This action somehow complements the cognitive perception of the experience. Even if the experience machine perfectly simulated the physical, emotional and mental highs and lows of training for a marathon and running the race, it seems we would still prefer to actually run the race ourselves. We don’t just want to know what it is like to run a marathon. We want to actually go out and pound the pavement for twenty-six miles.
Nozick adds, “A second reason for not plugging in is that we want to be a certain way, to be a certain sort of person. Someone floating in a tank is an indeterminate blob. There is no answer to the question of what a person is like who has been long in the tank.”  Part of the preference for actually running a marathon over the merely simulated experience is we want to be the kind of person capable of training for and completing a marathon. A person who experiences the simulated version of a marathon cannot be said to be the kind of person who runs a marathon in terms of qualities like perseverance, physical endurance, introspection and mental toughness. It is all but certain the experience machine user does not have those qualities in anywhere near the degree he would have them if he had run a marathon.
In short, there is a direct connection between doing and being. Performing courageous acts is what constitutes being brave. Demonstrating intelligence is what constitutes being smart. Moving heavy objects is what constitutes being strong.
To fully explore this connection, Nozick goes further: “Since the experience machine doesn’t meet our desire to be a certain way, imagine a transformation machine which transforms us into whatever sort of person we’d like to be (compatible with our staying us).”  And if that’s not enough, “Consider then the result machine, which produces in the world any result you would produce and injects your vector input into any joint activity.” 
“Perhaps what we desire is to live (an active verb) ourselves, in contact with reality.”
But still these new machines fall short of what we want out of life. A machine that magically makes us brave or smart or strong is insufficient. Instead, we actually want to perform acts of courage, intelligence or strength. And a machine that magically makes us perform those acts is hardly better. Rather, we actually want to perform those actions ourselves, of our own volition. As Nozick concludes, “Perhaps what we desire is to live (an active verb) ourselves, in contact with reality.” 
In other words, life (at least the one we want) requires physical action. We don’t want to just experience things in our minds. We want to physically do them, make our bodies do the work, feel physical pain and pleasure and enjoy the sense of achievement that comes from actually performing physical actions. And it doesn’t matter whether the activity in question is mental or physical. Having the experience of solving a complex mathematical theorem would not be enough. We would want to actually write down the equations, share the discovery with others, write a paper and get it published. Just like we’d rather run, jump or lift at the Olympics instead of just having the simulated experience of winning a gold medal.
But as Nozick points out, the experience machine puzzle also tells us something about morality. It’s not enough to respect an agent’s experiences. If it were, we wouldn’t get upset at the premise of The Matrix because there would be nothing wrong with hooking somebody up to an experience machine and using his body’s heat and electrical activity for energy.
Thus, physical bodies and physical actions matter to questions of morality. It’s not enough that others don’t infringe on our felt experiences. We don’t want them to infringe on our bodies or actions, even if we’re not aware of the effects of that infringement. And it’s not enough that we experience the virtuous feeling of being brave, intelligent or strong. We actually want to perform the virtuous actions that constitute being brave, intelligent and strong. To be fully moral human beings, we need our bodies and we need to perform physical actions. For that reason, it makes sense for us to take care of our bodies and prepare them to act.
- Nozick, Robert. Anarchy, State, and Utopia. New York: Basic Books, 1974, p. 42.
- Ibid, p. 43.
- Ibid, p. 44.
- Ibid, p. 45.