Thomas Hobbes’s account of will in Leviathan is a breakthrough because it explains voluntary action without inventing a voluntary faculty. But to understand it, we must begin where Hobbes begins — and he does not begin with will, or with movement in general. He begins with a problem: how does the external world act upon us without moving into us?

An object outside us does not travel into the eye or the ear. It does not enter the body. Yet it produces an effect within us. Hobbes’s answer is that the object presses upon the sense organ, and this pressure is transmitted inward as motion. The object does not move into us; it causes motion within us. Everything that follows in his account of passion, deliberation and will is a continuation of that inward motion.

Hobbes distinguishes two kinds of motion in a living body. Vital motion — the circulation of blood, the pulse, breathing, digestion, nutrition, excretion — begins with life itself and continues without requiring thought. Voluntary motion — walking, speaking, moving our limbs — begins with an idea in the mind of where, how, or what we intend to do.

But before voluntary motion becomes visible, something has already begun within us. Hobbes calls this small beginning of motion endeavour.

Endeavour has direction. When it is towards something, Hobbes calls it appetite. When it is away from something, he calls it aversion. These are not feelings or preferences. They are movements. To have an appetite is already to be moving towards something, even if the movement has not yet become visible action. To have an aversion is already to be moving away.

From these two directions Hobbes constructs the whole world of the passions. Love is appetite for something present; hate is aversion towards something present. Hope is appetite combined with expectation of obtaining; fear is aversion combined with expectation of harm. Confidence, despair, courage, anger, benevolence, pity, envy, grief, glory — all are treated as different forms and combinations of our movements towards what attracts us and away from what repels us, together with what we remember, expect, hope, or fear. Nothing new is introduced. The same motion, differently combined, produces the entire emotional life.

Hobbes’s treatment of good and evil follows the same approach. What a person has appetite towards, he calls good. What he has aversion towards, he calls evil. We ordinarily think we first recognise something as good and therefore have appetite towards it. Hobbes reverses the direction: we have appetite towards something, and it consequently appears good to us. At the level of individual motivation, the language of good and evil begins from appetite and aversion, not from a detached moral perception occurring first.

These movements frequently conflict. I may have appetite towards something while simultaneously having aversion towards its consequences. Appetite and aversion can succeed one another concerning the same action. Hobbes calls this succession deliberation.

Deliberation is not a rational judge sitting above the passions. The appetites and aversions themselves constitute the movement of deliberation. There is no separate faculty doing the deliberating. The deliberation is the alternation of the passions.

Eventually this process terminates. And it is here that Hobbes introduces will.

He gives an extraordinarily economical definition:

“Will therefore is the last Appetite in Deliberating.”

More precisely, it is the last appetite or aversion immediately preceding the doing of an action or its omission.

Hobbes is not introducing another mental faculty after deliberation. He is not saying that we first have appetite, then deliberate, then an independent entity called Will makes the decision. The final appetite or aversion with which deliberation terminates is what Hobbes calls the will. The name is given to the appetite or aversion with which deliberation ends. Nothing is added.

This explains Hobbes’s disagreement with the Scholastic tradition, which defined will as “rational appetite.” His objection is simple. If will necessarily means rational appetite, then there could be no voluntary action against reason. Yet human beings plainly do things they themselves know to be unreasonable. Reason tells me not to do something; I understand the consequences; nevertheless I do it. The action may have been unreasonable, but it was voluntary. If such action was voluntary, then voluntary action cannot by definition be rational action. Hobbes therefore refuses to make reason an essential ingredient of will.

This fits the wider direction of Leviathan. In the preceding chapter Hobbes treated reason not as a mysterious superior faculty but as a kind of reckoning or calculation. Here he performs a similar operation upon will. He does not need an invisible rational faculty sitting between appetite and action.

The account is mechanical in the sense that it explains voluntary action entirely through motion. Nothing is added that is not motion: the object pressing on the senses, the inward transmission of that pressure, endeavour, appetite, aversion, deliberation, will. There is no separate faculty of Will, and no rational power standing above the passions.

It is also important not to read a future-oriented choice into Hobbes’s account. Will is not a faculty that stands before multiple futures and selects one. It is the last appetite or aversion in a process that was already underway. The movement began with the external object acting on the senses, continued inward as endeavour, divided into appetite and aversion, alternated in deliberation, and now terminates in action or omission. Will is the terminus of that movement. It is the present resolution of a process that began outside us.

Will, for Hobbes, is therefore not a thing but an event — the event in which deliberation ends and action begins. It is not a state, not a faculty, and not a cause that produces action as a separate effect. It is the last appetite in a sequence, and action is the visible motion that follows.

Hobbes begins with the external world acting upon the senses, and he ends with the body acting upon the world. The will is the last appetite in the process that runs between them.