A efficient causeA efficient cause (e.g. the woodworking of a chair) was the name given by Aristotle to the top term in his tetrad of four causes, such that it and a final cause (e.g. the need for a chair) are required to mediate the formal cause (the idea of sitting) and material cause (e.g. the wood used) in order for something (like a chair) to be actualized. (e.g. the woodworking of a chair) was the name given by Aristotle to the top term in his tetrad of four causes, such that it and a final cause (e.g. the need for a chair) are required to mediate the formal causeA formal cause is a name given to the top term of Aristotle's tetrad of causes, such that it and a material cause require mediation from an efficient and a final cause in order for something to be actualized. (the idea of sitting) and material cause (e.g. the wood used) in order for something (like a chair) to be actualized.