Nature and origin of motion in Locke
In the secondary literature, one cannot find a study of how Locke addressed the issue of motion, of its nature and origin. With my essay I try to fill this gap, offering an overall analysis of the idea of motion in Locke’s Essay and in his subsequent writings. Locke discussed the topic from a psychological perspective, as he adopted in his natural philosophy the mechanistic hypothesis that motion is transmitted only by impulse. I examine Locke’s criticism of Descartes’ theory of matter and his revision of his own mechanistic view, following Newton’s theory of gravitation. My reconstruction focuses on the issue of the origin of motion that Locke defined within the metaphysical dualism of corporeal and incorporeal substances. Locke argues that the subjective experience of voluntary motions provides us with a clear idea of the origin of motion, while the observation of bodies allows us only to perceive its transmission. Locke ascribes to God the origin of motion in the universe, by analogy with its origin in spiritual finite substances. I will show how Locke maintained the long-standing metaphysical tenet of matter’s passivity, and of the origin of motion through the agency of self-moving spiritual substances. However, due to Locke’s psychological approach and his agnosticism on the real essence of substances, this conception loses its categorical certainty and becomes a weak analogical conjecture. Despite the conceptual difficulties besetting Locke’s view of the origin of motion, his theory is noteworthy as it shows how metaphysical categories, traditionally assumed as fundamental ontological presuppositions, originate from a limited psychophysical experience.