Letters 58.9

Now “man” is a species, as Aristotle says; so is “horse,” or “dog.” We must therefore discover some common bond for all these terms, one which embraces them and holds them subordinate to itself. And what is this? It is “animal.” And so there begins to be a genus “animal,” including all these terms, “man,” “horse,” and “dog.”

Seneca, Letters to Lucilius 58.9, translated by Richard Mott Gummere