Western philosophers since the modern era have tried to limit causation to relationships between physical actions, with Hume pointing out the unobservability of causal relationships directly. Salmon’s process theory attempts to address this by describing causal processes as spatiotemporal trajectories, but it is limited in its ability to account for aspects external to the physical world, such as norms and minds.
With the rise of the scientific worldview, Western philosophers since the modern era have tended to limit causation to relationships between physical actions. In doing so, philosophers began to emphasize scientific methodology and empirical evidence. The problem, as Hume pointed out, is that causation itself is not directly observable. We can only observe the events that are the cause and effect. For example, “The cold caused the river to freeze,” is not a statement of a directly observed physical fact. Hume’s skepticism took issue with this unobservability of causal connections, which led to doubts among philosophers about whether causation is a scientific concept.
Salmon’s process theory is an attempt to understand causation in terms of a scientific worldview. Salmon sought to overcome the limitations of traditional causal explanations. When you throw a baseball, the shadow of the ball on the ground moves with it. The shadow moved because the ball moved, not because the shadow itself moved and changed its position. Process theory explains this difference as follows. A process is the spatiotemporal trajectory of an object. A baseball in flight, as well as a ball resting on the ground, is on a spatiotemporal trajectory because time is passing. The state of the ball at rest is also a process. However, not all processes are causal. Some processes meet another process at a point in space and time, that is, they intersect. If the intersection introduces a signature, a changed physical property of the object, then the process that can carry that signature to all subsequent points is the causal process.
For example, let’s say a banana travels from point A to point B. Process 1 is the process of traveling from point A to point B. Process 2, which is taking a bite out of the banana at a point halfway between A and B, intersects with process 1. This intersection marker was introduced into process 1, and this marker can be transferred to B. In other words, the banana can continue traveling to B without losing the bite. Therefore, process 1 is a causal process. The movement of the banana is the cause of the effect of the banana being at B. On the other hand, suppose the banana’s shadow is cast on the screen. The process by which the banana’s shadow moves from point a′ to point b′ on the screen is called process 3. After the intersection of process 1 and process 2, the shadow on the screen also changes. But suppose process 4 intersects with process 3, in which a bumpy piece of Styrofoam is attached to a point on the surface of the screen between a′ and b′. As the shadow overlaps that point, the label distortion is introduced into process 3, but once the shadow passes through that point, the shadow returns to its original shape and the Styrofoam remains the same. In this way, process 3 cannot carry the label introduced by the intersection with another process.
A limitation of process theory is that it has difficulty explaining aspects outside of the physical world, such as norms and the mind. For example, there is a causal relationship between my violation of a social norm and my deserving of punishment, but process theory does not handle this well. To overcome these limitations, some philosophers have begun to explore new approaches to complement causal explanations. They have attempted to understand causal relationships in terms other than physical processes, and have proposed complex causal models that take into account social and psychological factors. This represents an important attempt to expand the scope of causal understanding.
