According to that doctrine, motives deprive us not of free-will, nor take away our power of performing or forbearing any action.

But according to common notions a man has no power, where very considerable motives lie betwixt him and the satisfaction of his desires, and determine him to forbear what he wishes to perform.

I do not think I have fallen into my enemy's power, when I see him pass me in the streets with a sword by his side, while I am unprovided of any weapon.

I know that the fear of the civil magistrate is as strong a restraint as any of iron, and that I am in as perfect safety as if he were chained or imprisoned.

But when a person acquires such an authority over me, that not only there is no external obstacle to his actions; but also that he may punish or reward me as he pleases, without any dread of punishment in his turn, I then attribute a full power to him, and consider myself as his subject or vassal.
Now if we compare these two cases, that of a person, who has very strong motives of interest or safety to forbear any action, and that of another, who lies under no such obligation, we shall find, according to the philosophy explained in the foregoing book, that the only known difference betwixt them lies in this, that in the former case we conclude from past experience, that the person never will perform that action, and in the latter, that he possibly or probably will perform it.
Nothing is more fluctuating and inconstant on many occasions, than the will of man; nor is there any thing but strong motives, which can give us an absolute certainty in pronouncing concerning any of his future actions.