"Despite Singer's proud affirmative statement that he has finally discovered the definitive solution to the problem of abortion and can finally settle the issue, his "proof" depends on many possible sub-arguments (which he prefers not to "see"). His pro-abortion argument can only be established if we accept some kind of utilitarian ethics according to which the well-being of concrete human beings is above any abstract or metaphysical idea of the "human person" (something that would make them "intrinsically valuable"). It also depends on the idea that what is ethically relevant is that humans do not suffer unnecessary pain, and on the thesis that a human being can be defined by a set of well-defined relevant properties (the famous "indicators of humanity"). It also depends on a very specific definition of the terms "homicide" and "innocent" in the expression "innocent human being", and on the deactivation of the idea of "potentiality", in the sense that someone can be potentially a thing at time t + 1, which would give him rights at t. It is a large number of assumptions without which the "objective" and "definitive" conclusion would not follow. Any debater who does not accept at least one of these assumptions will not accept Singer's "indisputable results". And contrary to what he says, those who do not accept them are not "simply wrong", but they assume other perfectly plausible, sustainable and rational assumptions and Gestalten within the network of arguments. Singer drastically ignores all the questions and obstacles in his line of argument (e.g., the controversy over "indicators of humanity"), and it is only in this way that he can still feed the illusion of having "solved" the problem of abortion."
January 1, 1970
https://en.wikiquote.org/wiki/Julio_Cabrera