A New Argument From Motion

The following is not an exposition or explanation of any argument found in the texts of Aristotle or Thomas Aquinas, but it is inspired by their work, and located within the tradition.

​Let's begin by assuming that all change must have a cause. Another word for ‘change’ in this context is ‘passion’. Let’s assume, then, that every passion has a corresponding action. On this picture, the action of the agent is the cause; the passion of the patient is the effect. Causation always involves two or more substances. Here we will also introduce a principle of proportionate causality. It is obvious, for example, that actual change or passion can only result from actual action, involving an actually existing agent and an actually possessed active power. A merely potential event cannot be the actual cause of any actual change. A merely potential agent cannot act.
 
If we were to abandon this principle of ontologically proportionate causality, we would have no explanation for the asymmetry and irreflexivity of causation. That is, we couldn’t explain why a given passion couldn’t be its own cause, promoting itself from mere potentiality to actuality. This would be tantamount to rejecting the causal principle altogether.
 
Every passion must be located in time, since time is the measure of change. What is the temporal relation (if any) between an action and its corresponding passion? There are four logical possibilities: (i) the action is earlier than the passion, (ii) the action and passion are simultaneous, (iii) the action is later than the passion, or (iv) the action is unlocated in time. I will argue that only cases (ii) and (iv) are metaphysically possible.
 
Let’s say that an entity is temporal when it has a state that is located in time. In cases (i) through (iii), the agent has a state (namely, the action) that is located in time, so the agent must be temporal. Only in case (iv) can we have an atemporal or timeless agent.
 
If an agent is temporal, then all its states are actual or potential only relative to the various moments of time (see Koons 2020, Koons forthcoming). Therefore, we cannot say that the agent’s action is actual simpliciter but only that it is actual or potential at this or that time. We must also adapt our principle of causality to incorporate this relativity: for each passion, its corresponding action must be actual at the time at which the passion occurs. Actions occurring in the past or future are, at the time of the passion, merely potential. Hence, we can rule out cases (i) and (iii).
 
Every change must have a cause. If a temporal agent A acts at time t to produce a passion in some patient, then agent A must have undergone some change that eventuated in this particular action at time t. The agent has changed from not being the agent of a particular change to being the actual agent of that change. Hence, the change in the state of the agent requires a cause.
 
If all agents were temporal, this would lead to at least one infinite causal regress at each moment of time. We could then consider the whole plurality of things undergoing change at that time and ask, What causes them to change? Since these changes are all simultaneous, nothing prevents us from aggregating them together into a single, massive event. Given the principle of causation, this simultaneous plurality of events must have a cause that is both separate from itself and actual (at t). Since the plurality includes all changes occurring at this time t, the only possible cause of the plurality of changes would be the action of an atemporal agent. An atemporal action can act at any or all times without undergoing any change itself, and so without requiring a cause.