Hobbes, Conatus and the Prisoner's Dilemma
I. Conatus and Motion
Philosophers in the 17th century made hard efforts to explain the beginning and continuation of the motion of bodies. The notion of conatus ('striving' or 'endeavoring') was commonly used in the explanations. It refers to the power with which the motion of a body begins and is kept on.
What is this power? Descartes explained it to be an active power or tendency of bodies to move, expressing the power of God. He distinguished between motion and the tendency to move, but Hobbes was anxious to argue that conatus actually is motion. In The Elements of Law he says it to be the "internal beginning of animal motion" (EL I.7.2), and in his later writings the notion of 'endeavor' refers to the beginning or first part of any kind of motion. Because motion is for Hobbes "a continual relinquishing of one place, and acquiring of another" (De Corp II.8.10), the beginning of a motion of a body must be an infinitely small change in the place of the body. Accordingly, Hobbes defines endeavor "to be motion made in less space and time than can be given; ... that is, motion made through the length of a point, and in an instant or point of time" (De Corp III.15.2).
For Hobbes, the conatus is not an inherent power of a body but is determined by the motions of other bodies. However, he regards it as an active power, because "the beginning of the motion of a body must be considered as action or cause" (De Corp II.9.6). Thus endeavor is the power by which a body affects the motion of other bodies and resists their power, and, in a sense, also 'causes' the motion of the body itself, for Hobbes takes the principle of the persistence of motion to be true: "whatsoever is moved, will always be moved in the same way, and with the same swiftness, if it be not hindered by some other moved and contiguous body" (De Corp III.15.1). Thus Hobbes, like Descartes and Spinoza, takes conatus to be the active power by which a body persists in its state of motion. In brief, Hobbes accepts the following fundamental principle:
This is a true natural law for Hobbes. I want to show the importance of (CP) for Hobbes's theory of human action and political philosophy.
II. The Beginning of Voluntary Motion
The following explanation is given in The Elements of Law for the beginning of a voluntary motion. The motion caused by an external object in the sense organ continues to the brain which resists it by its own endeavor to keep on the "vital motion" of the brain (EL I.2.8). The reaction of the brain is experienced as an "imagination" or "fancy", and imaginations tend to be preserved as "memories" even after the original external cause is removed, due to the conatus-power of the brain to keep its state on. This is the first clear application of the conatus-principle:
From the brain the imagination-motion proceeds to the heart that reacts by its active power or endeavor. When the motion strengthens the vital motion of the heart, delight or pleasure is generated, and because the vital power of the heart is decisive for the vitality of the whole human or animal body, then what we experience as delight or joy is nothing else than a motion increasing the active power or conatus of the heart. Correspondingly, any fancy or memory which weakens the vital motion of the heart is felt as pain or displeasure, or fear in case the displeasure is not present but expected (EL VII.1).
Here begins a voluntary motion: the emotion of pleasure or pain causes a motion toward or away from the external cause, and this motion "is the endeavor or internal beginning of animal motion" (EL I.7.2) which determines the direction and power of the voluntary motion. All human actions consist in this way "in appetite or aversion to or from the object moving" (ibid.). When we are deliberating, the possible consequences are represented as images in our brains, some of which cause desires and some aversions, and the vector sum of these various endeavors then determines the kind of action we will commit. The will consists of this sum total; it is "the last appetite in deliberating" (Lev, I.6; H 28). The will is therefore the desire which forms the conatus of a voluntary motion, and the motion initiated in this way continues until the power of new images causes a change in the conatus.
III. Reason and Passions
Hobbes explains emotions or "passions", as appetites or aversions of particular things (e.g., Lev I.6). They are closely connected with what Hobbes calls knowledge by experience, or prudence. The important feature of this kind of knowledge is that it is "regulated by some desire" (Lev I.3; H 9). Scientific knowledge, or knowledge by reason, is essentially different, although based on experience. Hobbes thinks that the world has certain universal and unchanging features, "accidents as are common to all bodies, that is, to all matter" (De Corp I.6.4), and these universal features are the causes of those conceptions we reach by 'ratiocination' and call universal laws of nature. The most universal common property is motion (De Corp I.6.5), and therefore we obtain knowledge of the true laws of nature when we come to know by ratiocination how the other universal properties are generated in terms of motion.
Hobbes must conceive reasoning, too, as a kind of motion having an external cause, but he gives it a special status: the causes of reasoning are features common to all bodies in the world, and they remain always the same, like the causes which generate a circle. Because the motions of reason are unaffected by any particular causes, we can understand why it is always free from passions, and being entirely free from resisting causes, they will have the same conatus forever. Perhaps this explains why Hobbes can think of reason as a motion and at the same time as the spring of eternal truths.
This of course is true of right reason only. Hobbes believed that whenever we follow reason, we cannot err or get into contradictions, and in this sense we can be entirely free. The will to reason and to follow its conclusions, laws of nature, might be called our rational conatus.
IV. Preservation of Life
Let us call the first motion, or compound of motions, with which the existence of a body begins, the initial endeavor. It is the power by which the body persists its existence. The initial endeavor of living beings appears as their power to preserve their life, and this they do "by a certain impulse of nature, no less than that whereby a stone moves downward" (De Cive I.8). This is perhaps the most important way Hobbes uses the principle of conatus.
(CP4) A living being endeavors to preserve its life and resist anything contrary to it.
According to Hobbes, this conclusion is a law of nature which all living beings follow by necessity.
It seems therefore odd that he speaks of the right to preserve one's life. He just wanted to say that anything that is in accordance with the laws of nature is done rightfully; "that which is not contrary to right reason, that all men account to be done justly, and with right" (De Cive I.8). In this way natural right is based on natural laws, and "[t]he first foundation of natural right is this, that every man as much in him lies endeavor to protect his life and members" (ibid.), i.e., the conatus-principle (CP4).
V. The Social Contract
By (CP4), we necessarily endeavor to preserve our life and resist anything contrary to it, and whatever the reason may show as a means to the preservation, we will try to accomplish with the same endeavor. Hobbes argues that certain important means can be found by right reasoning.
The first is that every man ought to endeavor peace (Lev I.14; H 64). This is a law of nature for Hobbes resulting as an important derivation of the conatus-principle:
The reason tells further that peace can be obtained only by acting for common ends. To attain peace, it is necessary to reach consent by making mutual contracts or covenants concerning how people use their will or power. In other words,
The third law of nature is "that men perform their covenants made" (Lev I.15; H 71). This is a natural consequence of the principle (CP6), because true covenants are declarations of will, and will again is the power by which a body preserves the motion of a voluntary action, as (CP2) says.
Because making contracts and keeping them are necessary means to attain peace, pointed out by reason, people desire them by equal power; the endeavor in (CP7) and (CP6) is the same as in (CP5).
The rational conatus has a double task: it makes men to find out the laws of nature, and it also makes them to establish a peaceful and just society. This is what Hobbes means by his famous words that "civil philosophy is demonstrable because we make the commonwealth ourselves" (SL; EW VII 184). We have to notice that passions play no role in the demonstration of a just society; indeed, they must not have any role, since the building of a just commonwealth depends on the rational conatus alone. According to Hobbes' theory of action, contracts may ensue only when the rational conatus of participants is stronger than the power of their desires resisting the will to covenant, and it must remain so in order for the contracts to be valid. Because this is not in general the case, (CP7) cannot be the only rule right reason tells to obey, but dictates another one:
This, like (CP7), is a law of nature. Both are principles of reason. What would be against reason is to break contracts because of following selfish passions or by fear of becoming attacked. Fear would not form a rational reason for us to follow war, although our behavior caused by fear would be in accordance with the law of nature that (CP8) renders.
VI. Hobbes and the Prisoner's Dilemma
Let P mean the peace-promoting behavior (making and keeping contracts), and let W mean the war-preserving behavior (refusing from making or keeping contracts). According to the commonplace view, the preference ordering of the Hobbesian players would define the Prisoner's Dilemma game:
Here the first member of each pair is 'my choice' and the second member the choice of 'the others'. (PD), however, would not accord with the principles of reason; specifically, the preference <W,P> <P,P> would violate the principle (CP7). (PD) would describe the preferences in a proper way if, and only if, all of the players were what Hobbes calls fiery spirits or fools. However, Hobbes's argument is essentially concerned with the situation of players who follow reason. What would their preference ordering be like?
Obviously, the mutual state of peace is the most desired thing: <P,P> <W,W>. By (CP7), according to which we endeavor to keep our contracts when there is no reason to suspect others, we obtain the preference <P,P> <W,P>. When people are led by the rational conatus, they do not desire to acquire advantages by breaking contracts when others behave peacefully. Alan Ryan remarks accurately that a Hobbesian man is not a utility maximizer but a disaster-avoider. By (CP8), we obtain the preference order <W,W> <P,W>, and everything else becomes fixed except the preference of the state <W,P> to <W,W>. For this preference we do not find an answer from Hobbes, for the simple reason that <W,P> is not any option at all for a Hobbesian man of reason. However, we might take it to describe a situation where a reasonable man occasionally suffers from weakness of will and, following his strong passions, breaks the mutual covenant. Obviously, we cannot suppose that Hobbes would have considered this kind of state worse than a mutual state of war, and therefore the final rational ordering of preferences will be as follows:
This defines a strategic situation called Assurance Game by Amartya Sen. Michael Taylor rejects this kind of interpretation of the Hobbesian situation, because "in this game there is no need for coercion to prevent a Pareto-inferior equilibrium occurring; mutual cooperation will occur without it". However, if we take into account that some people do not follow reason but passions, and have therefore the PD-preferences, the rational players are to live in a risky situation. They have only imperfect information of the preferences of the other players and no confident expectation that they will always choose P when contracted. What they need is assurance that a majority of the other people will play the same game they play.
VII. Conatus and the Hobbesian Sovereign
The Hobbesian sovereign is a 'body' to which the contracting participants convey an essential part of their power, that is, of their rational conatus as well as the means they have to support this conatus. Thus the power of the sovereign represents a combined conatus of citizens; it is like a big body that receives its force to move towards peace from many small bodies causing its motion.
(CP9) The sovereign endeavors to preserve the life of citizens by the joint conatus-power of rational individuals.
From this principle, Hobbes derives several interesting characteristics of the sovereign.
The power of the sovereign is absolute in the sense that there cannot be any greater power to limit it, because the sovereign already forms "the terminus ultimus of the forces of all the citizens together" (De Cive VI.13). The power is indivisible (Lev II.18; H 93), which it must be as it consists of one unified will. Hobbes also reminds that the sovereign power cannot be forfeited or resisted, for we cannot do that without contradicting ourselves: the sovereign power represents our rational will. As long as the power of the sovereign represents our rational conatus, it remains valid forever, and appears as the endeavor of the sovereign to preserve its being a sovereign. This implies the necessity of succession, or as Hobbes says, the "order of artificial eternity of life" of the sovereign (Lev II.19; H 99).
The phrase "artificial eternity" expresses well the power of the sovereign as an endeavor to preserve its state.