In Nicomachean Ethics (1097b) Aristotle says happiness is the highest good because we always choose it as an end in itself and never for the sake of anything else:
What is always chosen as an end in itself and never as a means to something else is called final in an unqualified sense. This description seems to apply to happiness above all else: for we always choose happiness as an end in itself and never for the sake of something else.
How is this so? How can we tell that the ultimate end for humans, from the perspective of our species, is what Aristotle calls “happiness”?
Honor, pleasure, intelligence, and all virtue we choose partly for themselves — for we would choose each of them even if no further advantage would accrue from them — but we also choose them partly for the sake of happiness. On the other hand, no one chooses happiness for the sake of honor, pleasure, and the like, nor as a means to anything at all.
Does that mean happiness is our god? And if we recognize that happiness is not God but that it too is subordinate to Him, is it appropriate for Him to be the means to that end, which Aristotle sets as the end? If not, what are we to do instead?
First let us try to understand what Aristotle means by “happiness”, the Greek term eudaimonia, which often is rendered as “human flourishing”. As implied by Aristotle above, “happiness” is not pleasure itself. If we are to recognize a purpose for humanity, happiness in this sense is fulfilling the reason for us to have been created. However, it is tautological to say that our end is attaining what we are here for.
Either we acknowledge a higher end from the perspective of a divine being, while we recognize our happiness as the highest end from our perspective, or we conclude that we ourselves and our happiness are the final end of everything, not just our own little lives. What our happiness is, is contingent upon our nature, i.e. what sets us apart as human, because “the prize and end of excellence and virtue is the best thing of all” (1099b) for us, which is happiness.
If we take the first, that from God’s perspective there is an end to our happiness, somehow our happiness must be embodied in and inseparable from that divine end. If so, we must also take our cues about our essence from Him who has made us human. So if there is a God who has purposes for us we cannot speak of happiness, or human flourishing, in isolation from we are made for.
The alternative is having been made by no sentient God. But if God exists, an intelligent being, then our lives must be worship to Him, because apart from Him there is no happiness.