The Parallel Curves of Will: Why Neuroscience Is Reviving a 17th-Century Puzzle About Agency

Your hand rises. You feel you made it happen. But according to Nicolas Malebranche, writing in the 1670s, the true cause was elsewhere. God, he argued, is the sole active power in the universe—every bodily motion, every sensation, is directly produced by divine will. Your intention is not the cause; it’s merely the occasion for God to act. This is occasionalism, and its central puzzle is how a mental event can be paired with a physical one without any causal bridge. Malebranche’s answer was a hidden geometry he called influxus—a lawful pattern of correspondence between mind and body, like two parallel curves that never intersect but follow the same rule. The concept, explored in the notion of “Parallel Curves” in the history of occasionalist thought, treats the mind-body relation as a synchronized dance scored by God, not a transfer of force. The idea that your intention and your action are two parallel curves that never intersect yet follow the same law—God’s synchronous song—is a surprisingly precise metaphor for what modern neuroscience finds. In Benjamin Libet’s readiness-potential experiments, brain activity that predicts a movement begins hundreds of milliseconds before subjects report a conscious decision. Daniel Wegner’s work on the illusion of conscious will suggests that the feeling of agency is a post-hoc inference, not the origin of the act. The conscious intention and the neural event are correlated, but the evidence for a direct causal arrow from the former to the latter is thin. They run in parallel. Influxus offers a conceptual tool for thinking about this pattern without defaulting to either “mind causes brain” or “brain causes mind.” The model is one of coordination without direct causation—precisely the kind of non-causal relationship that neural correlates of consciousness present. A specific instance of occasionalist law: when you hear a loud noise, your startle reflex is not caused by the sound entering your ears; in Malebranche’s universe, God directly produces the bodily flinch on the occasion of the auditory sensation. The sound and the flinch are two curves following the same divine rule. Replace God with lawful physical processes, and you have a rough sketch of how a neural event and a conscious experience might be yoked without one producing the other. Dismissing this as merely theological hand-waving misses its value as a structural model. Influxus is a framework for thinking about correlation when causation is either absent or distributed across a system—a situation that arises constantly in the study of complex systems, from brains to social networks. The geometry of parallel curves, drawn by a law external to the relata, remains a fertile way to hold the mind-body problem open instead of closing it prematurely.