The utilitarian premises can hardly be considered as the appropriate starting point of a valid ethical inquiry. There is a marked departure between the utilitarianism of bentham and js mill. For one, js mills, in defense of bentham, explains that 'happiness' varies not only quantitatively, but qualitatively as well -- that in the qualitative degrees of happiness, there exists both lower and higher forms of it.
And that the highest form of utilitarian pleasure resides in what he calls an internal sanction, the explanation of which coincides with kant's categorical imperative.