Not surprisingly, this philosophy was super attractive to some people ( Jeremy Bentham and John Stuart Mill were big proponents). But others found it limiting and soulless: can we really reason our way into being happy? And what about the people who aren't in the majority? Is it okay to sacrifice the happiness of a couple of people if it makes a whole crowd happy? (It's another version of the classic ethical dilemma : would you kill one person to save four?) And how are we supposed to get beyond playing favorites, and just making our loved ones and ourselves happy?
However, when co-authoring The Point of View of the Universe (2014), Singer shifted to the position that objective moral values do exist, and defends the 19th Century utilitarian philosopher Henry Sidgwick's view that objective morality can be derived from fundamental moral axioms that are knowable by reason. Additionally, he endorses Derek Parfit's view that there are object-given reasons for action.  Furthermore, Singer and de Lazari-Radek (the co-author of the book) argue that evolutionary debunking arguments can be used to demonstrate that it is more rational to take the impartial standpoint of "the point of view of the universe", as opposed to egoism—pursuing one's own self-interest—because the existence of egoism is more likely to be the product of evolution by natural selection, rather than because it is correct, whereas taking an impartial standpoint and equally considering the interests of all sentient beings is in conflict with what we would expect from natural selection, meaning that it is more likely that impartiality in ethics is the correct stance to pursue.