Aristotle's dispute with Plato over the manner of being proper to the eidē

Aristotle's dispute with the Platonic account of the eidē takes issue with its “separation” of the “beinghood” (ousia) belonging to a genos from the multitude of single things that are encompassed by it. For Aristotle, the answer to the question “Why do things look the same?” is not because there is an eidos of a highest rank, the genos, that encompasses everything that is, but because each one of the things that are is generated in some material (hulē) by an eidos whose proper mode of being is “being-at-work (energeia)” on it. The “beinghood” of things caused by the perpetual “being-at-work” of the eidos (without it ever undergoing change) is perceived and understood by the soul because the very “being-at-work” of an eidos responsible for generation also shapes the soul's perception and informs its understanding. The “beinghood” or, more properly within the context of Aristotle's metaphysics, “thinghood”, of things has its source in “nature” (phusis). Because of this, thinghood, together with eidos, hulē and phusis, are one in the generation (genesis) that perpetuates life (zōē) forever. The perpetuation of life through generation is therefore directed by the unchanging eidos whose manner of being is responsible at once for the generated thinghood of that which is and for the generations of generated things being informed by their eidē.