 species [force, power] is the first effect of an agent…the agent sends forth a species into the matter of the recipient, so that, through the species first produced, it can bring forth out of the potentiality of matter [of the recipient] the complete effect that it intends ([DMS], 6–7). This is a universal theory of natural causation as the background for his philosophy of vision and perception. Most importantly, species is a univocal product of the agent. The first immediate effect of any natural action is definite, specific, and uniform. This production is not the imparting or imposition of an external form. The effect of the species is to bring forth the form out of the active potency of the recipient matter. (DMS, 6–7)