Suppose the Utilitarian suggests that there is no logically possible world in which some act is morally wrong, and in which that act does not result in a depreciation of at least one creature’s ‘pleasure to pain’ ratio. I think this is a legitimate point, but I am not convinced that this alone would warrant Utilitarianism proposed as a model for weighing and measuring the moral character of our actions. Perhaps the intuition behind Utilitarianism is good insofar as happiness is sought for as the ultimate goal in moral actions, and happiness has something to do with pleasure, but happiness cannot simply be identified with pleasure. Indeed one person might live happier than another even while the other has more pleasure(s) in their life. For instance, it seems clear to me that the orthodox doctrine of Hell implies that people in Hell are happy in this Aristotelian sense, even while being in terrible agony (like the agony of losing the one you love even while being happy insofar as you are doing the right thing). It should be clear, though, that for Aristotle being happy consists in realizing the ends which are proper to some thing. Therefore, for example, a bee is happy to the extent that it realizes its natural ends, such as gathering pollen and producing honey. A human being’s happiness may include a psychological balance we can call contentment, but it isn’t restricted to anything as mundane as pleasure. A human being in more pain than another can be happier than the one not in pain.
Still, our moral actions have something to do with (have some necessary connection to) bringing about pleasure and stifling or eradicating pain. Perhaps that is because pleasure itself has something to do with this wider idea of happiness in this Aristotelian sense (later to be adopted and developed into a Christian doctrine of Happiness by Augustine, Boethius, and then finally by Aquinas who articulated a full Christian doctrine of mundane happiness). So, to be maximally happy includes having pleasure and not having pain. A (human) being is maximally happy only if that being experiences pleasure and does not experience pain.