1. (Science: psychology) That doctrine which refers all phenomena to a single ultimate constituent or agent; the opposite of dualism.
The doctrine has been held in three generic forms: matter and its phenomena have been explained as a modification of mind, involving an idealistic monism; or mind has been explained by and resolved into matter, giving a materialistic monism; or, thirdly, matter, mind, and their phenomena have been held to be manifestations or modifications of some one substance, like the substance of Spinoza, or a supposed unknown something of some evolutionists, which is capable of an objective and subjective aspect.
2. (Science: biology) See monogenesis.
Origin: From Gr. Single.