心身平行论(psychophysical parallelism)为二元论的一种，由希腊哲学家柏拉图所提出的二元并存理念所延伸出来的理论，认为人在表现出行为时，内在的心理活动与身体活动是同时产生的，两者是各自独立活动，并不会相互影响。此理论支持灵魂的存在，于文艺复兴时期，做为学者用来回避直接探讨灵魂存有于否的理论。

Psychophysical parallelism, in philosophy, is the theory that mental and bodily experiences occur in tandem with each other, but without any type of causal interaction; it denies the interaction between the body and the mind. In other words, the mind and body are two independent phenomena but cannot be separated from one another – like two sides of a coin. The theory is the third possible alternative in considering the relation between mind and body, the others being interaction and one-sided action, for example, materialism.