The theme of this paper is the sacred life value theory and its applicability to questions of practical ethics, especially to those related to environmental issues. The general aim consists in pointing the limits of DworkinÂ’s conception about the theory of sacred life, when applied to the environment, and in highlighting the solution offered by Singer, i.e.: the attribution of value to environment. This comparison is justified through the importance of discussing (starting with the analysis of these philosophical theories) the establishment of an ethical principle, to be used in the field of moral action, that takes into account not only all sensitive beings, but also the environment as a whole. Besides, the theme developed here contributes to the discussion of relevant ethical problems. This study approaches the question of the threshold between the beings who are included in the moral community and those who are excluded from it Â– also a relevant ethical problem. The traditional ways of classification are not able to include all the living in the moral community. There are always exclusions, which tend to decrease thanks to the rise of innovating ethical theories, like some of those which will be considered in this paper.