The question of the human person is very important for moral theology because of the possibility of responsible human action. Nevertheless, the old utilitarianism that already comes from the empiricist position of Hume reduces the calculation of costs and benefits to an evaluation of the pleasant/unpleasant of the individual subject. The new utilitarianism takes its inspiration from Bentham and Mill and can be summarized in a threefold injunction: maximizing pleasure, minimizing pain, and expanding the sphere of personal freedom for the greatest number of persons. One of the popular promoters of preference utilitarianism in modern times is the Australian ethicist Peter Singer, whose controversial views attracted much attention not only from the scientific community in the late 1970s. In this paper we will try to show a critique of this position in several figures of philosophical and theological ethics as well as a defence of the importance of the notion of the human person and human dignity for the integral protection of human life from conception to natural death and of anthropocentrism as such in respect for all creation and all of nature.