I think we'd agree happiness is not always the summum bonum. We can each, I think, imagine a very evil person who is happy in their evil, but is living badly. Perhaps likewise, a very good person, who is happy, yet something is missing from that.
But is happiness enough, if we are moral creatures?
In my experience, with such emphasis on duty or virtue, there's a sense in which happiness is itself irrelevant, and it's morality all the way down.
From the point of view of Neitzsche's "Genealogy of Morals" ethics is the history of changing the meaning of 'happiness' to suit the forces in each era that have the most to gain from controlling mass-cultural behavior.
One of his reactions to this is to use every one of the German synonyms for happiness for something more specific. Gaiety, cheer, joy, etc. all refer to real emotions with different physiological components. Merging them all into a single thing called happiness makes for something that the wily can make mean whatever they want.
The ascetic peace of the Anchorite is a form of happiness in submission to a purpose, that many ordinary folks would define as depression induced by boredom due to a limited worldview. But by their own standards, that is always enough.
He refers to the eventual mangled and diluted notion of natural happiness to which we are headed over time as these manipulations pile up as "wretched contentment", the "happiness" of satiation and stagnant luxury. Taking Sartre's analogy of nausea as the symptom of evading authentic freedom, this may always 'be enough' for us to live by, but it is also often just a bit too much for us to digest.
So, to answer the question with a question "When is what in particular enough?"
Because we thought of life by analogy with a journey – with a pilgrimage. Which had a serious purpose at the end and the thing was to get to that end; success or whatever it is or maybe heaven after you’re dead. But we missed the point the whole way along. It was a musical thing and you were supposed to sing and to dance while the music was being played. But you had to do that thing, you didn’t let it happen. - Alan Watts
I choose to open with this quote because it is ever-so-slightly not contrary to your position. In philosophy, there are answers to this question on all ends of the spectrum. There are philosophers who argue that there is no greater good than to suffer in this life to support the goodness that their religion dictates. There are indeed philosophers who not only argue that happiness is enough, but that personal pleasure is the highest calling there is. We call those hedonists. There's opinions everywhere inbetween. Every color under the sky.
And then there are those who argue that the distinctions we draw between these terms are not as permanently etched as we sometimes think they are. Some argue that we are climbing a tall mountain, and while everyone is trying their own different route, we're all climbing towards the same goal. Indeed, as we approach our "goal," if such a concept is even meaningful, we find the words blur together. The line between happiness and enlightenment blurs. Truth and good blurs. Beauty and morality blurs. They all start to blur together towards one concept.
And this leads some to wonder, if the words so blur at the destination, perhaps they are blurry even now, right where we are.
What else would you judge your progress on? All moral guides are about happiness in the end they only differ in the degree to which they postpone that happiness. Religious servitude is not done for the hell of it, it's done to get into heaven which is supposed to be a nice place in which you are happy. The virtues in virtue ethics are not arrived at randomly, they are those virtues which, if cultivated, will cause you most happiness in the long run. It is the means which differ, not the goal.
What most people mean when they say that morality or duty impedes on their happiness, is that it does so in the short-term, no-one could say whether a life of moral duty might lead to happiness in the long-term until that long-term has been lived, and even then, if you include an afterlife, it is still uncertain. This uncertainty does not disappear in the short-term, only diminish, you can't be certain that having that extra slice of cake will make you happy despite the fact that you know you "shouldn't". This is the reason why moral codes, virtues or duties evolved, to try and give some kind of guidance from experience where the long-term happiness gain is not obvious.
A hermit from a remote land with some sense of "mystical" wisdom might say the following (humor intended :):
Dichotomies that we face in life as in between desire vs virtue, happiness vs morality, individual vs collective good, — and we can go further on to include political dichotomies such as freedom vs rule of law, etc... — are all basically accidents of natural existence. In other words the principle of conflict and dichotomy is inherent in nature. So down from the microscopic level all the way to communal life of living organisms and up to the highest echelons of human politics, conflict is pervasive in nature!
From this it follows that so long as one's values are confined to nature one is destined to face all sorts of dilemmas in life where one can't gain something without losing something else. Constant dissatisfaction and stress, or a not-so-better (if not worse) alternative, that is, self-deluded happiness, or even worse an arrogant life of trying to achieve maximum good at the cost of others would be the inevitable outcome!
So what would be the way to freedom from this inherently dichotomic existence: the mystic would have it that it is for one to establish "an inner connection" (and stronger and stronger levels of that connection) to higher planes of existence where, quite interestingly, unity of opposites is possible!
It does sound so impressive of a theory and of a promise, but as with any other start-up in the natural world, there are costs and challenges! Realizing this lofty state would itself involve, on the negative side, relinquishing certain "mundane" goods for embracing a path that leads to a superior good. On the positive side the path involves a period of spiritual exercise involving moderation of desires, meditation, prayer, supplication, moral discipline which all work towards realizing that higher existence by just striving for it and concentrating our mental energy on it!
It all may seem too much indeed, but the greater obstacle is that inner voice saying that all this can't be true! But chances of certified belief can come from delving into various spiritual traditions in world major religions. My personal favorite to recommend would be Sufi tradition in Islam!
The question could be rephrased like:
Does happiness alone define a moral creature?
Or
Can a person be satisfied with only happiness and nothing else?
On one hand, happiness is not an independent state of well-being, so there is a dynamic between it and other things. You cannot isolate it, so the question doesn't make any ultimate sense, though intuitively it sounds trivial. On the other hand, modern philosophers like Viktor Frankl or Herbert Marcuse portrait negative aspects of current understandings about happiness. On such accounts, yes to the questionable role of happiness, non-intuitively.
For the other notions about duty and morality, we know for sure they are subjective or at least localized. If we see ourselves as just unremarkable elements in the Circle of Life, then duty is more important than morality simply because it's omnipresent.
The first priority should be to investigate what happiness means. Usually it means something like, experiences we want. So, is happiness enough becomes, is getting experiences we like enough? A tautology, that contributes nothing. In that definition, anything that brings happiness is what we want, and anything we want brings happiness. If 'it's' not enough, nothing is.
Aristotle's concept of eudaimonia is often translated as happiness, but that obscures a much more sophisticated concept. They say it translates better as 'human flourishing', or more literally as 'a spirit of good guardianship over one's being'. Aristotle's idea of multiple material souls, 'organisational essences', see's the differently levels of organisation as seeking flourishing on different levels, bodily in nourishment, sensorily in pleasure stimulation and desire, and cognitively through polis and philosophy.
Reifying happiness and unhappiness as correlates of pleasure and pain, leads into negative utilitarianism. It a nihilist position, that on balance pleasures do not balance out pains.
I like Alan Watts on why 'Happiness is not the meaning of life' https://m.youtube.com/watch?v=RsdoJ9x8IBs
Was recently discussing cultures that put more emphasis on duty to family than personal material success, and how it seems that emphasis relate to putting more value on education, and wider notions of wellbeing than material ones. Virtue can't just be an individual behaviour. It is an 'uncool' area of philosophy now, the nature of virtue, but perhaps never more in need of reclaiming.
