I tend to ask several short-answer questions on my tests. Here is some guidance as to the level of detail that is likely to be required of your answers. The following answers are in response to this question: “What is the relevance, to ethics, of psychological egoism?”
1. Here’s a good answer:
“The relevance is that morality often requires one to act non-self-interestedly, and this would be impossible if psychological egoism were true. So ethics would lose much of its point if psychological egoism were true.”
2. Here are a couple of answers that are too short:
“Psychological egoism says that non-self-interested action is impossible.”
“Morality often requires one to act non-self-interestedly.”
3. And here is an answer that is unnecessarily long:
“Psychological egoism is the view that every action is motivated by self-interest. It does not say that people ought to act self-interestedly, only that they always do. Therefore, if psychological egoism were true, then people would never act non-self-interestedly. Ethics says that people ought to sometimes act non-self-interestedly. For example, most people agree that it would be immoral to tamper with other people’s medicine even if it would make one happy. Ethics does not require you to always act non-self-interestedly, but it sometimes does. But psychological egoism says this is impossible. Therefore, if psychological egoism were true, then it would often be impossible for people to act ethically.”