§46. The Sensible Motions of the Mind
Thomas Hobbes is an “empiricist” of the same stripe as Aristotle, and he is no friend of experiments in natural philosophy, which he considered futile. He was an older contemporary of Boyle, and they apparently loathed each other.
Boyle's friends at the Royal Society felt Hobbes's contempt for their experiments and refused him entree. Hobbes belongs to the story of empiricism as a minimal empiricist, who looks more to logic than experience for his science. We meet his type again in Rudolf Carnap (§66).181Hobbes awakened to natural philosophy and made his first effort, a “Short Tract on First Principles,” during a sojourn in Paris, 1634-36. He was forty- five, and tutor to a scion of the Cavendish family, with whom he was associated since obtaining his Oxford BA in 1607. He had learned Italian and was in Italy at the time of Galileo's first celebrity with the publication of Siderius nuncius in 1610. By the Paris years he had conceived the idea of combining a theory of sense as the original power of cognition with a reduction of the act of sense to matter in motion, thereby reducing psychology and epistemology to physics. Since he would elsewhere reduce politics to psychology, it made a tidy system.
Materialism has always had difficulty negotiating the transition from natural causes to consciousness. To perceive is to perceive qualities, and nobody has ever explained how quantitative, mechanical change translates into the qualities of perception. Boyle was working on the problem, but that was little comfort to Hobbes, and besides Boyle, for all his mechanism, was not a reliable materialist, and not averse to an incorporeal spirit for a pious cause. Hobbes is untroubled by the supposed gap between consciousness and body.
He seems to think, as Boyle did, that the explanation of change in terms of motion is inherently intelligible (both learned it from Galileo).
Since the act of sense is real and the foundation of cognition, it has to admit of explanation in terms of motion. So the act of sense is a motion, even if Hobbes has no idea which motion.Hobbes attacks the objectivity of sensible qualities and the existence of an immaterial soul with an energy unequaled since Lucretius. Everything is corporeal, even the soul—“being and body are the same.” Even God—“God is a body.” Yet his metaphysics is less a materialism than a kineticism. All things reduce to matter, but what propels him beyond Epicurus is that matter reduces to motion. Enduring extensive magnitude is not an accident in a substance. Accidents do not exist; they are not bodies, and what we take for a continuous body is an image. “Things themselves do not persist through change, but only their images and looks.” Spatial extension is a phantasm, an image, an effect of resonant motion in the perceiving body. Size and therefore space resolve into motion within, a proposition waiting for Berkeley to discover. The essence of body is not mere abstract extension, as Descartes thought. It is extending, moving, a kinetic form, with motion joining matter’s primary qualities (as it had in Democritus). This is the climax of Hobbes’s natural philosophy, and a point on which he is followed by Spinoza, Leibniz, and Diderot.182
Hobbes studied Aristotle for five years at Oxford, graduating with a qualification to lecture on the logical treatises. It is good to remember that his first expertise was Aristotle’s logic. With all the Aristotelians, he affirms “there is no conception in a man’s mind which hath not at first, totally or by parts, been begotten upon the organs of sense.” The controversy concerns the details. How exactly does physical change produce a conception in the mind? Aristotle refuted the mechanism Democritus began when he introduced eidola, semblances flowing between the distal object and the sensory surface. Ockham shuddered at the skeptical problems cognitive mediation raises, and avoided them with his theory of intuitive cognition.
Hobbes ignores these subtleties and returns to the simplified Aristotelianism he and Descartes modernize. Sense is a phantasm; cognition is mediated by representations, called by Hobbes thoughts, cogitations, and in his first work, species, channeling Roger Bacon. These are mechanical effects that environing objects “worketh on the eyes, ears, and other parts of man’s body,” and by their diversity of working “produceth diversity of appearances.”183The act of sense is the fundamental cognitive phenomenon, since only through it do we become aware of any other. Hobbes writes, “If the appearances be the principles [arche, starting point] by which we know all other things, we must needs acknowledge sense to be the principle by which we know those principles, and that all the knowledge we can have is derived from it.” He divides mental powers into sense, imagination, and understanding. The terminology is traditional, but not the explanation. Differences among these powers are merely quantitative; they are continuous developments of each other, and all are basically sense, which is basically motion. Imagination, of which memory is a special case, is defined as decaying sense, and understanding is imagination organized by words.184
As for sense itself, the fans et origo of consciousness and knowledge, it is cerebral vibration instigated by external motion. “In sense, that which is really within us, is... only motion, caused by the action of external objects.” A quality like color or heat is a vibration in the affected brain. “In the object that causeth them,” these qualities are “but so many several motions of the matter, by which it presseth our organs diversely. Neither in us that are pressed are they anything else but diverse motions (for motion produceth nothing but motion).” He urges the contribution of sense, but the rationale is rationalism. Every mutation is a motion, therefore sensible qualities are motions, “for motion produceth nothing but motion.” He does not need to explain the unknown mechanism by which motions in things become qualities of perception in order to draw his conclusion that sensory qualities are quantitative changes.
They have to be; the alternative is incomprehensible.185If sense is vibration in a body caused by proximity to other vibrating bodies, would that not make all bodies sensitive, conscious, ensouled? Hobbes allows the conclusion, closing distance with Spinoza and Leibniz. The difference between an animal body and a stone is that the animal's reactions are remembered. Unlike a stone, an animal has organs fit for retaining some of the motion generated in them by interaction with external things. In animal bodies the motion that instigates the phantasm-reaction remains and allows the phantasm to return. There is a phantasm in the stone—a reverberation— but no sense, not because it lacks a soul but from natural differences in the effect of motion on matter so formatted. That distinguishes animals from stones, but what distinguishes human beings from other animals is the ability to associate phantasms with names. “The discerning faculties of man leaveth all community with beasts at the faculty of impressing names.” With names, we no longer need the sensations—their actual cause—to think about their objects. We can reason concerning sensible bodies in their absence and plan our interaction.186