UC Davis Philosophy 22 Lecture Notes

Thomas Hobbes

Picture of Thomas Hobbes

Thomas Hobbes (1588-1679) is best known for his political philosophy, particularly as found in his classic Leviathan (1651). He also wrote extensively on natural science, particularly optics. In metaphysics and philosophy of mind, his main work was De Corpore, or Concerning Body (1656). Hobbes was one of the critics to whom Descartes's Meditations was sent by Mersenne for comment, which resulted in the Third Objections and Descartes's replies to them. Descartes has been quoted as saying that Hobbes was "extremely contemptible" for daring to criticize him. In fact, Hobbes's point of view was so opposed to Descartes's that most of the exchange was unfruitful.


Hobbes conceived of philosophy as treating, in progression, three subjects: bodies, human beings, and commonwealth. Together they make up the three sections of his Elements of Philosophy. This ordering in based on his view that human beings are animated rational bodies, and that the commonwealth is composed of human beings. (The illustration below from the title page of the 1839 edition of Leviathan captures the relation of the sovereign to his subjects: his body is composed of those of the people he governs.)

Illustration of the King's body composed of his subjects' bodies

We will here focus on the first section, body, though from Hobbes's description, it is clear that the treatise Concerning Body involves more than physics.

In the first part of this section, which is entitled Logic, I set up the light of reason. In the second, which hath for title the Grounds of Philosophy, I distinguish the most common notions by accurate definitions, for the avoiding of confusion and obscurity. The third part concerns the expansion of space, that is Geometry. The fourth contains the Motion of the Stars, together with the doctrine of sensible qualities. (Author's Epistle to the Reader)
Parts three and four cover many of the same topics that were treated by Descartes in such works as Optics, Geometry, Meteorology and Principles of Philosophy. There are numerous differences between Hobbes's and Descartes's treatment of these matters, but the Hobbesian doctrines which profoundly conflict with the Cartesian are found in the first two parts.

In the Introduction to Part I, "Computation or Logic," Hobbes gave a definition of philosophy.

PHILOSOPHY is such knowledge of effects or appearances, as we acquire from true rationcination from the knowledge we have of their first causes or generation; And again, of such causes or generations as may be from knowing first their effects.
All philosophy, then, reduces to causal reasoning from effects to causes or causes to effects, where the effects are appearances of things to the senses. So we might begin with the fact that a body is moving and reason that its motion is caused by its being an animal, which has a faculty of moving on its own. Or, going in the other direction, we may reason that what appears to be circular really is a circle by knowing that it was produced with a compass. The goal of philosophy is to use our knowledge of causes to produce the effects we desire.
The end of knowledge is power; and the use of theorems (which, among geometricians, serve for the finding our of properties) is for the construction of problems; and, lastly, the scope of all speculation is the performance of some action, or thing to be done. (Concerning Body, Part I, Introduction)
The products of philosophy are various arts: those of measuring matter and motion, moving heavy bodies, architecture, navigation, instrumentation, etc., all of which are of immense value. Theology, however, is excluded from philosophy, since no generation can be conceived in God.


Reasoning, for Hobbes, is computation: the manipulation of symbols. The symbols themselves are "names," which are "marks" to ourselves of conceptions we have had and "signs" to others that we have had those conceptions. Conceptions, in turn, are "phantasms" or mental images which ultimately derive from sense-perception. Names allow us to organize our own thoughts and to communicate them to others. They do not designate objects directly, so that the name "stone" is the sign of a stone only insofar as that "he that hears it collects he that pronounces it thinks of a stone" (Concerning Body, Part I, Chapter 2, Section 5). The upshot of this indirect account of reference is that names do not signify "the matter or form, or something compounded of both, and other like subtleties of the metaphysics" (Section 5). Indeed, a name need not signify anything at all.

An important type of name is the "universal name," which is "the name of many things severally taken, but not collectively of all together" (Section 9). That is, a name like "man" signifies the conceptions of a number of individual things "as of Peter, John, and the rest severally" (Section 9). A universal name does not pick out a "universal," or a thing in which all the individuals share. Instead, it functions in a general way. Hobbes says that "universal" is a "name of a name," in that it indicates the way in which a name is used.

[S]o that when a living creature, a stone, a spirit, or any other thing is said to be universal, it is not to be understood, that any man, stone, &c. ever was or can be universal, but only that these words, living creature, stone &c. are universal names, that is names common to many things; and the conceptions answering them in our mind, are the images and phantasms of several living creatures or other living things. (Section 9)
Compare this view with that of Descartes, who held that our conception (or "idea") of, say, a triangle, signifies a real nature, which does not require the existence of any individual triangle, and whose properties we can know with certainty (Meditation Five). Hobbes claimed, on the contrary, that the name "definition" signifies only "what we think of the nature of things," rather than the nature itself (Section 10). Because he refused to allow names to signify things, and in particular denied that universal names signify universal things, Hobbes can be called a "nominalist."

Another important category of names is the "compounded name," such as "man." This name is composed of other names. We begin with the simple name "body" and add to it a name, "animated," for a second conception that we form when we see the body move. We thus form the compounded name "animal," which means "animated body." When we hear the body speak intelligibly, we add "rational" to "animal" (or "animated body") and get the further-compounded name "rational animated body," or "man." "And by this we see how the composition of conceptions in the mind is answerable to the composition of names" (Section 14). We must not, however, make the mistake of thinking that the objects indirectly signified by the compounded names are compounded in the same way:

namely, that there is in nature a body, or any other imaginable thing existent, which at the first has no magnitude, and then, by the addition of magnitude, comes to have quantity, and by more or less quantity to have density or rarity; and again, by the addition of figure, to be figurate, and after this, by the injection of light or colour, to become lucid or colured; though such has been the philosophy of many" (Section 14).
The properties of a thing are separable from them only in thought, or when the thing changes.


The doctrine of method is the final part of logic, falling after the discussion of names, propositions, and inferences. The starting point of philosophy is "the phantasms of senses and imagination; and that there be such phantasms we know well enough by nature" (Concerning Body, Part I, Chapter 6, Section 1). Philosophy begins with thought or ratiocination, concerning the causes of these effects.

METHOD, therefore, in the study of philosophy, is the shortest way of finding out effects by their known causes, or of causes by their known effects. (Section 1)
We know the effect when we know There are two methods whereby these things can be discovered, the "analytical" or "resolutive," and the "synthetical" or "compositive," which correspond to the two ways of thinking--dividing and composing names, respectively. We begin with what is best known to us and proceed to what is lesser-known. Following Aristotle, Hobbes held that what is best known "to us" is through sense-perception and what is best known "to nature" is what is best known by reason. Resolution or analysis generally is called for when something is known through sense-perception :
In knowledge by sense, the whole object is more known, than any part thereof; as when we see a man, the conception or whole idea of that man is first or more known, than the particular ideas of his being figurate, animate, and rational. (Section 1)
Note that these are not literal parts of a man, like arms and legs, but "parts of his nature." The kind of knowledge we get by beginning with the whole idea is knowledge of existence, "that any thing is" (Section 2).

Scientific knowledge is knowledge of causes, and here we know better the parts of things. We have a better understanding of the way in which the parts are caused because when they are compounded into a whole, their interactions must be taken into account. Composition or synthesis is what Hobbes calls the process of showing how a whole is compounded from its parts.

If our aim in investigation is to discover some particular piece of information, for example, "in what manner particular causes ought to be compounded for the production ofsome certain effect," either method might be called upon. But if we want to discover the causes of all things, we need to know the accidents (or properties) that are common to all bodies, and this is acquired by resolution. "And in this manner, by resolving continually, we may come to know what those things are, whose causes being first known severally, and afterwards compounded, bring us to the knowledge of singular things" (Section 5).

When the process of resolution is carried out as far as it can go, we are left with one cause, motion. That this is the cause of the most basic properties of bodies ("universal things," as Hobbes puts it), is something that is "manifest" of itself, and hence needs no method.

For the variety of all figures arises out of the variety of thoses motions by which they are made; and motion cannot be understood to have any other cause besides motion; nor has the variety of those things we perceive by sense, as of colours, sounds, savorus, &c. any other cause than motion, as that it is manifestly some kind of motion, though we cannot, without ratiocination, come to know what kind. (Section 5)
Science proceeds by showing how the composition of motions leads to various effects: "what motion makes a straight line, and what a circular; what motion thrusts, what draws, and by what way; what makes a thing which is seen or heard, to be seen or heard sometimes in one manner, sometimes in another" (Section 6). The composition of these motions is treated most basically in geometry, and then is extended to physics (visible, then internal and invisible motions), psychology (motions in the human body) and politics (motions by groups of people). In general, analysis is what gives us general principles and synthesis is the application of the principles.

In pursuing his physics, Hobbes passed over the issue of the ultimate cause of the motions we observe. He noted that "the universal doctrine of philosophy" requires that one determine issues such as this:

if [the world] had a beginning, then by what cause and of what matter it was made; and again, from whence that cause and that matter had their being, will be new questions; till at last we come to one or many eternal cause or causes. (Part IV, Chapter 26, Section 1)
But these questions cannot be answered by a finite mind, because such a mind can have no conception of the infinite, and because the questions themselves can be answered coherently in different ways. "To questions therefore about the magnitude and beginning of the world, are not to be determined by philosophers, but by those that are lawfully authorized to order the worship of God" (Section 1). Hobbes chose to restrict himself to matters which "it is not unlawful to dispute of."


The task of philosophy is to discover the causes of effects and to infer effects from causes. Motion is the primary explanatory principle of the behavior of bodies: it is the cause. But what is a cause? It is, not surprisingly, a combination of accidents or properties in the things acting (agents) and the things acted upon (patients). These properties must be sufficient for bringing about the effect ("all which existing together, it cannot be understood but that the effect existeth") as well as necessary for bringing the effect about ("it cannot be understood but . . . that it can possibly exist if any one of them be absent").

Hobbes gives an extended example of the cause of light, which includes a source of light, a medium, and the human body, all of which, when they are in the right conditions, cannot help but bring about the existence of the light (through motion, of course). "And in this manner the cause of light may be made up of motion continued from the original of the same motion, to the original of vital motion, light being nothing but the alteration of vital motion, made by the impression upon it of the motion continued from the object" (Section 10). To know the cause of a human being, the method requires that we find the causes of each of his "parts," that is, of body, of animation, and of rationality.

Hobbes compared his conception of causality with the Aristotelian doctrine. According to Aristotle, there are four ways in which something might be considered a cause: as the source of change (efficient cause), as the material changed (material cause), as the essence or nature (formal cause) and as the goal or end of the process of change (final cause). Descartes had eliminated final causes from explanations of the physical world, on the ground that God's intentions are unfathomable (Meditation Four). Still, he appealed to essences or natures as explanatory. Most importantly, Descartes held that we can explain God's existence by appeal to his nature.

Though in his explanations Hobbes appeals to "natures," i.e., the "universal parts" which make things up, these parts are not themselves causes. Only aggregates of accidents are causes. Thus Hobbes reduced the causes to two, what he called the efficient cause and the material cause. As we have seen, he analyzed every causal connection into two elements, the agent and the patient: that which changes by its motion and that whose motion is changes. The agent is identified with the efficient cause and the patient with the material cause.

After discrediting Aristotle's notions of formal and final causes, Hobbes gave them a new interpretation. A formal cause is uninformative. Say that the nature of man is rational animal. Then to say that rational is the cause of man is just to say that man is the cause of man, since man is rational. The proper role of rational is as a ground of knowledge: I know that this animal is a man because it speaks intelligently, and hence is rational. Final causes exist only insofar as human action is guided by desires. A group of people build a church because they wish to have a place of worship. But desires are really only motions, and so they are (through the bodily motions they initiate) efficient causes of the building of the church.


This scheme of causes through motion was accompanied by a hard determinism, that is, the view that every event which occurs is the necessary outcome of a prior cause, and consequently that the human will is not free. Determinism with respect to what is caused stems from Hobbes' definition of causality, as those accidents which, taken together, are sufficient to bring about a change in another set of accidents. If a change occurs, the conditions were sufficient to bring about that change, and so it must have occurred. If it does not occur, then there were no conditions sufficient to bring about its change, "without which the act cannot be produced; wherefore that act shall never be produced; that is, that act is IMPOSSIBLE: and every act, which is not impossible, is POSSIBLE" (Section 4). So, for Hobbes, whatever has a cause is necessary and whatever lacks a cause is impossible. What we call "contingent" changes are simply those of whose causes we are ignorant.

The only way to avoid determinism, on this view of causality, is to allow that changes can take place without a cause. For Hobbes, all change is a change in motion, and he firmly rejected the idea that motion can take place in any way other than by being caused by motion.

For as for those that say anything may be moved or produced by itself, by species, by its own power, by substantial forms, by incorporeal substance, by instinct, by antiperistasis, by antipathy, sympathy, occult quality, and other empty words of schoolmen, their saying so is to no purpose. (Part IV, Chapter 30, Conclusion)
Human activity was reduced by Hobbes to motion, so it gets caught in the net. Whatever we will is determined, since willing explained in terms appetites and desires, which themselves are motions. The only sense in which humans are free is that we sometimes can do what we want to do. But what we want to do is determined, since it too is explained in terms of bodily motion.

Hobbes was engaged in a drawn-out dispute with Bishop Bramhall over the issue of free will. Against a barrage of attacks, he steadfastly maintained his position that "no man hath his future will in his own present power," but that whatever we will is determined by present circumstances (The Questions concerning Liberty, Necessity and Chance, concluding section).

The will is not free, but subject to change by the operation of extrenal causes, [and] all external causes depend necessarily on God Almighty, who worketh in us both to wil and to do, by the mediation of second causes. (Liberty, Necessity and Chance, concluding section)
A man can be said to be free in that he can do what he wills to do and can refrain from doing what he does not will to do. This so-called "hypothetical liberty" was to be advocated later by David Hume in his Enquiry Concerning Human Understanding, Section VIII.


Hobbes was reviled as an atheist by many of his contemporaries and successors. We have already seen how Hobbes rejected natural religion in favor of faith in the case of the origin of the world. In his political philosophy, he traced the power of the sovereign to the desire of the governed to be protected, and not to the favor of the Almighty. He noted that clergymen took offense at the fact that "I make the supremacy in matters of religion to reside in the civil sovereign" (Liberty, Necessity, and Chance, concluding section). In general, Hobbes strictly segregated his explanations of the natural from appeals to the supernatural, though he was not above quoting Scripture to his advantage.

Moreover, Hobbes denied that "natural" reason can give us any determinate idea of God. It can only supply us with "negative attributes, as infinite, eternal, incomprehensible; or superlatives, such as most high, most great and the like; or indefinite, as good, just, holy, creator" (Leviathan, Part II, Chapter XXXI). The only effect of these words is to encourage obedience, respect, piety, and other appropriate religious attitudes. They are not really descriptive because human conception is not capable of comprehending the divine: "there is but one name to signify our conception of his nature, and that is I AM."

In "An Answer to Bishop Bramhall," Hobbes defended himself vigorously against the charge of atheism leveled by that clergyman. One basis for the charge was "because, I say that God is a spirit, but corporeal." After defending himself on scriptural grounds, Hobbes claimed that someone who holds that God is incorporeal, wholly in one place and wholly everywhere, may be an "atheist by consequence," since he destroys the unity, infinity and simplicity of God. This claim also applies to those, like the Bishop, who affirm human free will in light of divine foreknowledge.

Hobbes and Descartes

The replies made by Descartes to Hobbes are largely useless. Hobbes held that all conception is based on sense-perception, the thesis whose refutation is the central task of the Meditations. The whole discussion is practically moot because of this root disagreement.

As an illustration of the sterility of the exchange, consider Hobbes's criticisms of Descartes's two arguments for the existence of God. In the case of the causal argument of the Third Meditation, Hobbes questioned whether we possess of an idea of God, and claimed that God is inconceivable. Descartes concedes that if an idea can only be an image, the objection is effective. But he repeatedly tries to distinguish between an image and a "pure mental concept" and asserts that we have a pure mental concept of God. Here is how Descartes ended the exchange: "When it is said that we cannot conceive God, to conceive means to comprehend adequately. For the rest, I am tired of repeating how it is that we can have an idea of God. There is nothing in these objections that invalidates my demonstrations."

Regarding the ontological argument of the Fifth Meditation, Hobbes objected to Descartes's claim that our idea of God corresponds to a real nature of God. As we have seen, "natures," according to Hobbes, are conceived only from our sense-perceptions of existing things. The "nature" exists only so long as the thing exists: only the name remains when the thing perishes. So "essence without existence is a fiction of our mind." Though Hobbes did not state this explicitly, it seems reasonable to conclude from his account of natures that to say that God has a nature presupposes that God exists and cannot be used to prove it. To this Descartes responds, "The distinction between essence and existence is known to all. . . ."

[ Previous Lecture Notes | Next Lecture Notes | Menu of Lecture Notes | Philosophy 22 Home Page ]