I cannot recall whether this was in Oderberg's "Real Essentialism"[0] or Gilson's "From Aristotle to Darwin and Back Again"[1], but in one of the two, I believe

I cannot recall whether this was in Oderberg's "Real Essentialism"[0] or Gilson's "From Aristotle to Darwin and Back Again"[1], but in one of the two, I believe the author cites Maritain's view that there is essentially only one species of living things (in addition to human beings, whom Maritain, of course, recognized as possessing rational faculties, faculties that by their nature transcend non-intellectual life). This would seem to avoid the various questions about speciation and how it is possible, and certainly where there exists such ostensible radical potentiality for producing such variation along a lineage over time. And this agrees with the former book, in which Oderberg distinguishes between a phylogenetic understanding of species, and an ontological understanding. The traditional ontological definition for "human" is "rational animal". It is composed of the genus "animal" and the specific difference "rational" that differentiates the human species from among the other species in the genus "animal"[2]. Under this traditional way of defining species, rational life on other planets would, therefore, qualify as human. "The aliens" would be, in some sense, "one of us", even if they were to differ phylogenetically. This becomes quite interesting in the context of an analysis along the lines of Aristotle's "De Anima", as, for example, rationality has definite entailments when it comes to anatomy and physiology. [0] https://a.co/d/aL0An6N https://a.co/d/aL0An6N [1] https://a.co/d/hMKWLjm https://a.co/d/hMKWLjm [2] I am using the terms "genus" and "species" in the relative, ontological, intensional sense[3], not the narrow biological sense, as more or less meaning "broader category" and "narrower subcategory", respectively. Thus, we can say that the species of triangle is a plane figure that has three straight bounding sides, where "plane figure" is the genus, while having three straight bounding sides is the specific difference. [3] https://en.wikipedia.org/wiki/Genus%E2%80%93differentia_definition https://en.wikipedia.org/wiki/Genus%E2%80%93differentia_defi...