  Explanations often specify entities beyond the role played by the matter and the form of the entity itself. These cases are grouped by Aristotle as efficient or moving causes on the one hand and as final causes on the other. Efficient causes operate in a straightforward manner by initiating processes and bringing about their effects, whereas final causes account for processes and entities by being what these processes and entities are for, what they objectively intend to  attain.[7]    The fact that the role of efficient causes is not identical to that of the matter and the form of the entity whose features they are to explain does not require that every instance of efficient causation must issue from outside the entity moved.  On the contrary, an efficient cause can also be internal. In cases in which the efficient cause is internal, it will be, in its specific function, one of the parts, or even the formal aspect, of the entity caused to move.