The main goal of this paper is to reconstruct David Hume’s theory of action from the perspective of the second book Of the Passion in his work A Treatise of Human Nature. My paper will proceed in three steps. In the first part I present the main assumptions of Hume’s views on action together with a general outline of his theory. I show that for Hume action has a uniform character and that there is a constant relation between action and the motive which can be understood as desire or aversion. Next, in the second part, the main elements involved in the process of human activity will be outlined, such as: passions, will, liberty, and reason. Although Hume emphasizes that the passions are the main motive of action, since they have the power to initiate and withhold action, reason also plays an important role. In order to come to a better understanding, I will consider the functions which these elements are playing in human action and some of the problematic issues which are connected with them such as, whether each of the passions can motivate a person to action, what the relationship between passions and will is, and what kind of relation between passions and reason can be found. Finally, in the third and last part of my paper, I will conclude with a schematic outline of human action and the relation between different components engaged in the process of action.