Ask him if he has any life goals.

Of course, at age 8, he is unlikely to have very realistic life goals (if any) - and settling too strongly on any goal you have at that age may even be harmful, since it will be based on rather limited information. That said, it would be useful to have some driving goal in one's life. Meta-goals such as "I should learn things as broadly as possible, so that I will be in a position to do whatever I want when I do figure out my real life goals" are probably the most useful at this point, if he can be made excited about them. Having him read What You'll Wish You'd Have Known may help with that.