In efficient causality a distinction can be made between the “principal cause” and the “instrumental cause.” We say that a sculptor is the principal cause of a marble statue, because he is the ultimate explanation for its existence. But he is not the only explanation, for he needed tools to make the statue. In an important sense those tools caused the statue, albeit in a subordinate way—as instruments in the hands of the sculptor. The instruments are the means through which a principal efficient cause brings about a certain effect.
