And if, exactly in proportion as human beings raise their heads out of the slough of selfishness, they do not with one voice answer 'immoral', let the morality of the principle of utility be for ever condemned." Henry Sidgwick also considers the implications of utilitarianism for nonhuman animals. He writes: "We have next to consider who the 'all' are, whose happiness is to be taken into account. Are we to extend our concern to all the beings capable of pleasure and pain whose feelings are affected by our conduct? or are we to confine our view to human happiness? The former view is the one adopted by Bentham and Mill, and (I believe) by the Utilitarian school generally: and is obviously most in accordance with the universality that is characteristic of their principle ... it seems arbitrary and unreasonable to exclude from the end, as so conceived, any pleasure of any sentient being." Among contemporary utilitarian philosophers, Peter Singer is especially known for arguing that the well-being of all sentient beings ought to be given equal consideration. Singer suggests that rights are conferred according to the level of a creature's self-awareness, regardless of their species. He adds that humans tend to be speciesist (discriminatory against non-humans) in ethical matters, and argues that, in utilitarianism, speciesism cannot be justified as there is no rational distinction that can be made between the suffering of humans and the suffering of nonhuman animals; all suffering ought to be reduced. Singer writes: "The racist violates the principle of equality by giving greater weight to the interests of members of his own race, when there is a clash between their interests and the interests of those of another race. Similarly the speciesist allows the interests of his own species to override the greater interests of members of other species. The pattern is the same in each case ... Most human beings are speciesists." In his 1990 edition of Animal Liberation, Peter Singer said that he no longer ate oysters and mussels, because although the creatures might not suffer, there was a possibility they may and it was easy to avoid eating them in any case. This view still might be contrasted with deep ecology, which holds that an intrinsic value is attached to all forms of life and nature, whether currently assumed to be sentient or not. According to utilitarianism, the forms of life that are