Under the first head there are eight points of inquiry: 

(1) Whether it belongs to man to act for an end?

(2) Whether this is proper to the rational nature?

(3) Whether a man’s actions are specified by their end?

(4) Whether there is any last end of human life?

(5) Whether one man can have several last ends?

(6) Whether man ordains all to the last end?

(7) Whether all men have the same last end?

(8) Whether all other creatures concur with man in that last end?
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First article [I-ii, Q. 1, Art. 1]

Whether It Belongs to Man to Act for an End?

Objection 1:  It would seem that it does not belong to man to act for an end.  For a cause is naturally first.  But an end, in its very name, implies something that is last.  Therefore an end is not a cause.  But that for which a man acts, is the cause of his action; since this preposition “for” indicates a relation of causality.  Therefore it does not belong to man to act for an end.

Obj. 2:  Further, that which is itself the last end is not for an end.  But in some cases the last end is an action, as the Philosopher states (Ethic. i, 1).  Therefore man does not do everything for an end.

Obj. 3:  Further, then does a man seem to act for an end, when he acts deliberately.  But man does many things without deliberation, sometimes not even thinking of what he is doing; for instance when one moves one’s foot or hand, or scratches one’s beard, while intent on something else.  Therefore man does not do everything for an end.

On the contrary, All things contained in a genus are derived from the principle of that genus.  Now the end is the principle in human operations, as the Philosopher states (Phys. ii, 9).  Therefore it belongs to man to do everything for an end.

I answer that, Of actions done by man those alone are properly called “human,” which are proper to man as man.  Now man differs from irrational animals in this, that he is master of his actions.  Wherefore those actions alone are properly called human, of which man is master.  Now man is master of his actions through his reason and will; whence, too, the free-will is defined as “the faculty and will of reason.”  Therefore those actions are properly called human which proceed from a deliberate will.  And if any other actions are found in man, they can be called actions “of a man,” but not properly “human” actions, since they are not proper to man as man.  Now it is clear that whatever actions proceed from a power, are caused by that power in accordance with the nature of its object.  But the object of the will is the end and the good.  Therefore all human actions must be for an end.

Reply Obj. 1:  Although the end be last in the order of execution, yet it is first in the order of the agent’s intention.  And it is this way that it is a cause.