To understand most important ideas in psychology, you need to understand how the mind is divided into parts that sometimes conflict. We assume that there is one person in each body, but in some ways we are each more like a committee whose members have been thrown together to do a job, but who often find themselves working at cross purposes.
I think sociologists are among the best at thinking about emergence, of thinking about the ways that the society is more than the sum of the individuals. And I've found that much of the wisest writing on human social nature comes from sociology and anthropology, not from my own field of social psychology.
We scientists have way too much a tendency to simplify problems. I guess it actually comes to us naturally. Take the simplest unit, separate out all the confusing, external factors. Study it. Make sure you understand it. And in psychology that means the person studying the individual. But if you want to study our social nature, if you want to study processes that will lead to war and peace, you don't learn all that much by looking at the single individual. A lot of the important things are emergent facts about us, things that you can only see when you get a lot of us interacting.
Psychotherapy can help some people, especially people who are neurotic, who are always making problems for themselves. We are like a rider on an elephant. We can steer the elephant, and if he's not busy, he'll go where we want, but if he has other desires, he'll go where he wants. They need to get a better relationship between the rider and the elephant. In part, you get it just from watching yourself stumble around in life, make mistakes, then read a little psychology and stop blaming yourself. Realize that I am flawed. I am complicated. I am divided, and I'm doing the best I can.
I think that moral philosophy is useful for framing questions, but terrible at answering them. I think moral psychology is booming right now, and we're making a lot of progress on understanding how we actually work, what our moral nature is.
In college, I was dead set on being a philosophy major, because I wanted to figure out the meaning of life. Four years later I realized philosophy had really nothing to say about the meaning of life, and psychology and literature are really where it's at.