The two-axis model

It's quite common, when talking about happiness and sadness, pleasure and pain, good and bad, to place both options on either end of a single axis. Let's say you're a sentient computer of some kind. Somewhere within you is a number for how good or bad you feel, with 0 as neutral, -5 as a bit bad, and +100 as the best ever. This is very elegant, and seems to feel intuitively correct. If someone is sad, you want to make them happy to stop them from being sad. Or if something bad happens, you might try to do something nice to make up for it.

However, I believe the one-axis model is not sufficient. Things can be both good and bad, and a thing that has both significant positive and negative consequences (say, bombing Japan in World War 2) can hardly be equivalent to something with no consequences. We don't accept the idea that if you go out and save someone's life, that gives you one free murder. I think a better mapping to reality is a two-axis model, where good and bad are considered independently.

Similarly, a feeling of mixed happiness and sadness is of course possible and quite different from neutral. It is possible to cheer someone up when they feel bad, but I'm not convinced that the mechanism is by the happy feelings subtracting from the sad feelings. You can also distract someone from sadness with anger, pain, or mindless internet clicking. And it's true that just feeling like you're being cared for is soothing but, I should stress, that's not the same thing as enjoyable.

I once heard that as the difference between compulsion and desire: you want to go to the park because it brings you pleasure, but you are compelled to scratch an itch because not doing so brings you discomfort. For that reason, although you might describe a pleasurable feeling of relief when you scratch an itch, it is not real pleasure. The proof of this is simple: would you choose to be itchy?

Another place this shows up is reinforcement learning. The original one-axis model of reinforcement was just reward vs punishment, but it was later revised to have two axes: positive/negative and punishment/reinforcement. Positive and negative in this case should be read as additive and subtractive, so a smack is a positive punishment, because it adds something bad. A negative reinforcement takes away something bad. You can also have the opposite: a negative punishment takes away something good, and a positive reinforcement gives something good. These are four distinct ways to influence behaviour in this model, with different consequences for each.

And that is the thing I think is most important: not that two-axis is better in some abstract theoretical way, but that it has better consequences. If you go around thinking good is the opposite of bad, you're liable to wonder strange things like "nothing is bad in my life, why aren't I happy?".

Of course, the two-axis model makes that obvious: pleasure isn't anti-pain, and you would be happier with more pleasure and more pain than none of either.