Volition, or the act of willing, is often used to illustrate the causal relationship between mental events and physical events because it is a mental event that can directly cause a physical event, such as the movement of a body part.

David Hume argued that mental events are not causes of physical events, but rather are epiphenomena that accompany them. He based this argument on the principle of causality, which states that every event has a cause. Hume argued that mental events cannot be causes of physical events because they do not have the power to produce them.

René Descartes argued that mental events are causes of physical events, and that the mind is a non-physical substance that interacts with the physical world. He based this argument on the principle of conservation of momentum, which states that the total momentum of a system remains constant. Descartes argued that if mental events were not causes of physical events, then the total momentum of the system would not remain constant.

Behaviorism is a psychological theory that posits that mental events are caused by physical events, and that the mind is a product of the brain. Behaviorists argue that mental events cannot be studied directly, but can only be inferred from observable behavior.

Functionalism is a psychological theory that posits that mental events are caused by physical events, but that the mind is not reducible to the brain. Functionalists argue that mental events are defined by their function, and that they can be implemented in a variety of different physical systems.

Emergentism is a psychological theory that posits that mental events are caused by physical events, and that the mind is an emergent property of the brain. Emergentists argue that mental events are not reducible to the physical events that cause them, but that they arise from the complex interactions of these physical events.

Chaos Theory is a psychological theory that posits that mental events are caused by physical events, and that the mind is a self-organizing system. Chaos theorists argue that the mind is a complex system that is constantly changing and adapting, and that it is impossible to predict its behavior with certainty.

Quantum Psychology is a psychological theory that posits that mental events are caused by physical events, and that the mind is a quantum system. Quantum psychologists argue that the mind is a complex system that cannot be understood using classical physics, and that it is necessary to use quantum mechanics to understand its behavior.

Holographic Psychology is a psychological theory that posits that mental events are caused by physical events, and that the mind is a holographic system. Holographic psychologists argue that the mind is a complex system that is stored in a distributed fashion throughout the brain, and that it can be accessed from any point in the brain.

Non-Local Psychology is a psychological theory that posits that mental events are caused by physical events, and that the mind is a non-local system. Non-local psychologists argue that the mind is a complex system that is not confined to the brain, and that it can interact with other minds and with the environment in a non-local fashion.

Panpsychism is a psychological theory that posits that mental events are caused by physical events, and that the mind is a panpsychist system. Panpsychists argue that consciousness is a fundamental property of matter, and that all matter has some degree of consciousness.

Dualism is a psychological theory that posits that mental events are caused by physical events, and that the mind is a dualist system. Dualists argue that the mind is a non-physical substance that is separate from the physical body.

Materialism is a psychological theory that posits that mental events are caused by physical events, and that the mind is a materialist system. Materialists argue that the mind is a product of the brain, and that it is composed of matter.

Phenomenology is a psychological theory that posits that mental events are caused by physical events, and that the mind is a phenomenological system. Phenomenologists argue that the mind is a subjective experience that cannot be reduced to physical events.

Transcendentalism is a psychological theory that posits that mental events are caused by physical events, and that the mind is a transcendental system. Transcendentalists argue that the mind is a priori, and that it is not dependent on experience.