It is really laughable to see what different ideas are prominent in various naturalists' minds, when they speak of species; in some, resemblance is everything and descent of little weight—in some, resemblance seems to go for nothing, and Creation the reigning idea—in some, descent is the key,—in some, sterility an unfailing test, with others it is not worth a farthing. It all comes from trying to define the undefinable. Sometimes this is played out under "Structural Realism" in which a theory structure is true, but the objects it poses which are unobservable may or may not be real, so long as the theory is empirically adequate in other ways. But most of all it explains something about science. The important thing was that it was the overall organization of the organisms that defined them as a species, so long as it was reproduced. Ray's definition was not based on Aristotle or any logical system, but upon observation.