What ought you to do if you are uncertain about which moral theory is correct? Plausibly, this depends on whether and how we can compare values across different theories. In this paper, I shall defend an answer to this latter question – viz., the view that moral theories posit value on an absolute scale, and are thus straightforwardly comparable. I shall then consider the implications of this view for our moral reasons to ‘do the most good’ in the ways in which effective altruists typically try to do so (e.g., following long-termism). I shall suggest that on this view, much more than on others, you ought to give weight to these reasons even if you antecedently find it implausible that they exist.