In Welfare, Happiness, and Ethics, L.W. Sumner defends two significant constraints on one’s theory of welfare: formality and generality. An adequate theory of welfare, claims Sumner, must give a constitutive account of the “good-for” relation. This constitutive account must be sufficiently general that any entity whose status as a welfare subject is uncontroversial falls within its scope. This paper will argue that Sumner’s proposed constraints are particularly significant to utilitarian arguments for the equal moral considerability of non-human animals. In the absence of these constraints, the inconsistency that is alleged to follow from denying moral considerability to non-human animals, while affirming it for humans, fails to obtain. I will focus on Peter Singer’s argument for the equal moral considerability of non-human animals, in order to support the conclusion that questions about the formality and generality of welfare are significant areas of further research for philosophers of animal welfare.