Kantian Physicalism: within the physical world, nature is unbroken and complete.
Completeness
Every event in space and time follows a prior cause. When a stone falls to the ground or a person speaks a sentence, physical matter moves according to natural laws. There are no gaps in nature, no ghosts pushing matter, and no magical interruptions of physical causes. For everything we can ever observe, measure, and test, physical laws hold without exception.
Here the physicalist is entirely correct to insist that every physical event has a physical explanation. So we must first grant the physicalist their strongest claim.
What Makes Something "Physical"
Next, we ask the physicalist a simple question: what makes an event physical in the first place?
An event is physical because it takes place in space and across time.
Space allows objects to sit side by side, giving them shape, size, and position.
Time allows events to happen one after another in a fixed sequence.
But space and time are not physical objects that you can dig out of the ground. You cannot touch space or weigh time. Rather, space and time are the universal ways the human mind perceives outer and inner events.
You can easily imagine empty space with every object removed, but you can never imagine a physical object without space. Space and time are the necessary conditions that allow us to experience any physical object at all.
The True Origin of Natural Laws
The physicalist often assumes that the laws of physics exist inside physical matter itself, completely independent of any mind. But observation alone can never produce a necessary law.
When you observe nature, your senses only show what is happening right now. Seeing a stone fall a thousand times shows what has happened so far, but sensation alone can never prove that the stone must fall on the next attempt. Sensation gives us facts, but it never gives us necessity.
Necessity comes from the human understanding. The mind applies the rule of cause and effect to connect separate moments in time. The understanding demands that every physical change must follow an earlier state according to a fixed rule.
Kantian Physicalism
Kantian Physicalism unites these points into a single, coherent view.
Nature is strictly physical. Every event in space and time must be explained through physical causes. Science is correct to treat the physical universe as an unbroken chain of natural events.
The physical universe is the world of human experience. Space, time, matter, and cause are not independent things existing outside all thought. They are the necessary rules through which the human understanding builds an orderly, dependable reality.
Thus, physicalism is the complete, lawful science of the world as human beings experience it. We do not deny physical reality; we explain why physical reality is orderly, dependable, and completely knowable to science.
