To answer the OP, however, I'll just work from personal experience here rather than get overly philosophical. I agree with @Fidicen, though, that the dopamine route is somehow an unsatisfying answer to this question. Especially since the question is, 'what's the highest form of pleasure'? I'm not sure how we're defining 'high' here (like a moral category or a question of magnitude?). Anyway I'll just add a few personal experiences that aren't love: 1) I know I felt incredible when I got a very high mark for an undergraduate essay I wrote. It was after a period where the university doubted my ability to complete the course (personal problems), and my ambition at that point to become an academic historian would have sounded to them actually ridiculous (I'd had to retake both first year and second year). In any case, when I got the essay back, I had a feeling of the most overwhelming vindication and achievement. It was really quite 'triumphal', and to this day has its own soundtrack in my memory because of the music I was listening to at the time (Tchaikovsky's swelling finale to his 5th symphony). 2) Eureka moments are always quite nice, especially those times where everything seems to 'come together'. 3) Last winter, I suddenly realised that I was 'happy', after a very very long time of being unhappy. It was more a realisation that every aspect of my life was OK, but mostly the social side and the fact that I knew I was being true to my own principles (courage, integrity, &c.). It's not that I wasn't before, but just didn't get the opportunities of having them 'tested'. That realisation of happiness was very profound indeed. It had been about 8-9 years by that time since I could say it. Ultimately, I think the 'highest firm of pleasure' is something near to 'contentment'; the sense of general wellness you get when many aspects of your life are in order, when you're doing right by people, when you're working and producing excellence, when you feel that you have earned the genuine respect and friendship of others.