Self-interest

We have made it clear that everything we do is in our own self-interest. This is not necessarily in our best-interest. There are many examples, such as smoking, which disprove this theory. But just as ripping money, which is a piece of paper with value, you are fulfilling your self-interest to show the class something and achieve pleasure. Everything we do is to fulfill our desired. I would not say it is necessarily to achieve happiness, but some sort of pleasure. This would explain why some people inflict suffering. This may be pleasurable to them, although I find that hard to believe. But it is their desire, and they want to fulfill it. It definitely is not in their own best-interest.  They do not look at it this way though. Best-interest at this point does not matter, but self-interest does. Humans are proven to be selfish, and this is just another example.