The Greek word usually translated as happiness — eudaimonia — meant something closer to flourishing or living well, and it was assessed over a whole life rather than reported in a moment. Aristotle thought you could not confidently call a life happy until it was over, which sounds strange until you notice he is answering a different question from "how are you feeling?"
That ambiguity persists. When someone asks whether you are happy, they might mean your current emotional state, your general satisfaction with how things are going, or whether your life is genuinely good. These come apart in ways that matter. Someone in a comfortable but pointless job may feel fine and be missing something. Someone doing demanding, worthwhile work may be exhausted and be doing well.
Theories of wellbeingWhat actually makes a life go well.
Hedonism answers: pleasure, and the absence of pain. It has real appeal — pleasure is plainly good and pain plainly bad, and the theory explains why we care about wellbeing at all. Its difficulty is Nozick's experience machine. Offered a lifetime of perfectly simulated pleasure indistinguishable from reality, most people decline, which suggests we value something beyond how our life feels from inside.
Desire-satisfaction answers: getting what you want. This handles the experience machine easily, since what you want is to actually accomplish things, not to seem to. It also respects that people differ. But not every desire seems to make your life better when satisfied — desires based on false beliefs, desires you would abandon on reflection, desires for things that never touch your life at all. Refining the theory to exclude these tends to smuggle in a standard of what is genuinely good, which is what the theory was trying to avoid.
Objective-list theories answer: certain things benefit you regardless of your attitude toward them — typically knowledge, close relationships, achievement, autonomy, and health. This captures the intuition that a person absorbed in something trivial is missing out even if perfectly content. The standard objection is the obvious one: who decides the list, and is it not presumptuous to tell someone their life is going badly when they report otherwise? Defenders reply that we make such judgements constantly and think them reasonable — we hope for more than contentment for the people we love.
What research addsAnd what it can't settle.
Empirical work on wellbeing has found some consistent patterns: relationships matter a great deal, income raises reported wellbeing sharply at low levels and much less thereafter, and people adapt to many changes more completely than they expect. This is genuinely useful and it does not resolve the philosophical question, because the studies must decide what to measure before they can measure it. A survey asking how satisfied you feel is already assuming that satisfaction is the thing that matters — which is one of the contested positions, not a neutral starting point.
Most philosophers now hold some hybrid view: that pleasure matters but is not all that matters, that getting what you want matters when the wanting is informed, and that certain goods contribute to a life going well independently of whether they are enjoyed. That is less tidy than any single theory, and it is probably closer to what most people actually believe when they think carefully about someone they love.