The Conceivability of Mechanism

1 BY I am going to understand a special application of physical determinism-namely, to all organisms with neurological systems, including human beings. The version of mechanism I wish to study assumes a neurophysiological theory which is adequate to explain and predict all movements of human bodies except those caused by outside forces. The human body is assumed to be as complete a causal system as is a gasoline engine. Neurological states and processes are conceived to be correlated by general laws with the mechanisms that produce movements. Chemical and electrical changes in the nervous tissue of the body are assumed to cause muscle contractions, which in turn cause movements such as blinking, breathing, and puckering of the lips, as well as movements of fingers, limbs, and head. Such movements are sometimes produced by forces (pushes and pulls) applied externally to the body. If someone forced my arm up over my head, the theory could not explain that movement of my arm. But it could explain any movement not due to an external push or pull. It could explain, and predict, the movements that occur when a person signals a taxi, plays chess, writes an essay, or walks to the store.1 It is assumed that the neurophysiological system of the human body is subject to various kinds of stimulation. Changes of temperature or pressure in the environment; sounds, odors; the ingestion of foods and liquids: all these will have an effect on the nerve pulses that turn on the movement-producing mechanisms of the body. 2. The neurophysiological theory we are envisaging would, as said, be rich enough to provide systematic causal explanations of all bodily movements not due to external physical causes. These explanations should be understood as stating sufficient conditions