This article identifies empirical, conceptual and normative avenues to advance the speciesism debate. First, I highlight the application of Evolutionary Debunking Arguments (EDAs) as one such avenue: especially where (anti-)speciesist positions heavily rely on appeals to moral intuition, and EDAs have potential to move the debate forward. Second, an avenue for conceptual progress is the delineation of speciesism from other views in its vicinity, specifically from the view that biological differences between species are sometimes morally relevant ('species-relativism'). Third, if we adopt Singer's definition of speciesism, then a limitation of the current debate is that it is not obvious whether the core ethical principle that underlies anti-speciesist positions-the Principle of Equal Consideration of Interests-is widely applicable. Arguably, the interests of animals are often too dissimilar to establish what equal consideration amounts to. I underscore the need for integrating philosophical and empirical research, to come to terms with the extent to which the interests of members of different species are alike, and with the question of whether any dissimilarities might be morally relevant.
Keywords: Bernard Williams; Peter Singer; Shelly Kagan; cumulative culture; evolutionary debunking arguments; intuition; moral psychology; species-relativism; speciesism.