The efficient cause is a philosophical concept proposed by Aristotle. This is the agent which brings something about, for example, in the case of a statue, it is the person chiseling away, and the act of chiseling, 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.

There are 4 main causes of nature in Aristotle's view:

• the material cause,
• the efficient cause,
• the formal cause, and
• the final cause.

Saint Thomas Aquinas also refers to the four causes in his writings about the existence of God. "If there be no first cause among efficient causes, then there will be no ultimate, nor intermediate cause...Therefore it is necessary to admit a first efficient cause, to which everyone gives the name of God." (Excerpt from Summa Theologica Third Article: Whether God exists?)

See also

• Anthropic principle
• Causality

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