The Expansion of Ethics Circle in Peter Singer's Viewpoint

Theories of biology about evolution of the human and his physical and mental structure had broad influences on the field of ethics. The purpose of this study is the explanation and analysis of Peter Singer's view on the expanding of ethics circle based on biological and rational foundations of universal ethics.
In this narrative research, Singer's view on the expanding of ethics circle was analyzed and interperated.
Findings: Emphasizing on the principles of impartiality and equality, possibility of overcoming reason on demands of biological nature, singer believes that the origin of our moral attitudes is our biological nature, but in decision makeing, one must contemplate on common moral norms. In Singer's viewpoint, limiting impartiality to human species is an arbitrary action without any rational support; the criterion of this impartial consideration is the "ability of suffering and experiencing of pleasure" and accordingly he expands the circle of ethics in so far as it includes "most" of the animals and not all of them. There is some criticisms to him such as lack of attention to the weakness of reason and human tendencies, lack of separation between the epistemological and logical function of reason in the expanding of altruism, disregarding to preferences of all creatures in expanding the circle of ethics.
Singer's view is a moderate one; he believes that biology only caused to reflections on moral intuitions, but it cannot determine our moral norms. Accordingly, we can provide a universal and impartial ethics devoid of biological biases.