Can we achieve "pure" altruism?
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Existence of sociopathy - argument against altruism being in our nature
Altruism is an advanced form of natural selection among the same species
Feinberg's egoist vs. psychological egoism
Joel Feinberg. "Psychological Egoism." in "Reason and Responsibility: Readings in Some Basic Problems of Philosophy" 3rd ed. Joel Feinberg, ed. Enciono, CA: Dickenson, 1975. 501-512.505.
 Duncan-Jones, Austin. Butler's Moral Philosophy. London: Penguin, 1952.,p.96
Feinberg, Joel. "Psychological Egoism." In Reason & Responsibility: Readings in Some Basic Problems of Philosophy, edited by Joel Feinberg and Russ Shafer-Landau, 520-532. California: Thomson Wadsworth, 2008., p.521
Garvin, Lucius F. C. A Modern Introduction to Ethics. Boston: Houghton Mifflin, 1953.,p.512f
Ibid, ref.3, p.522
Judith Lichtenberg and “the possibility of pure altruism”
Most probably multifactorial; there can be no 'pure altruism'