Efficient cause is a concept used by Aristotle. It is perceived to be the immediate force or precursor of all existence with the respect to the existence of a universe. That view eliminates a prime mover because no prime mover could be honestly or intellectually conceived. The need for a first cause generates the meaning of God.

This is the agent which brings something about, for example, in the case of a statue, it is the person chiselling away, and the act of chiselling, that causes the statue. This answers the question, how does it happen? It is the sort of answer we usually expect when we ask about cause; the thing which happened to bring about certain results.

Philosophical concepts | Aristotle