Action is sometimes terminated to some product, sometimes not. When action is terminated to some product, the effort of the agent tends to the same. When action is not terminated to any product, the effort of the agent tends to the action itself. Every agent therefore must intend some end in his action, sometimes the action itself, sometimes something produced by the action. Therefore every agent acts to some end.
Actions are open to criticism only so far as they are taken to be done as means to some end.
It is not imputed as a fault to any one, if he fails in effecting that for which his work is not intended. A physician is found fault with if he fails in healing, but not a builder or a grammarian. Therefore both the natural agent, and the agent who acts according to art and with a conscious purpose, acts for an end. To an agent that did not tend to any definite effect, all effects would be indifferent. Every agent therefore tends to some definite effect, and that is called its end.