  This notion of all things as being evolved psycho-physical unities of some sort places Peirce well within the sphere of what might be called “the grand old-fashioned metaphysicians,” along with such thinkers as Plato, Aristotle, Aquinas, Spinoza, Leibniz, Hegel, Schopenhauer, Whitehead, et al. Some contemporary philosophers might be inclined to reject Peirce out of hand upon discovering this fact. Others might find his notion of psycho-physical unities not so very offputting or indeed even attractive. What is crucial is that Peirce argued that mind pervades all of nature in varying degrees: it is not found merely in the most advanced animal species.