Hobbes on Law, Nature, and Reason

The reason of a thing is not to bee inquired after till you are sure the thing it selfe bee soe. Wee comonly are att (What's the reason of it?) before wee are sure of the thing. T'was an excellent question of my Lady Cotton, when Sr. Robert Cotton was magnifying of a shoe, w^ch was Moses's or Noahs, & Wondering att the strange shape & fashion of it: but, M^r . Cotton, sayes shee, are you sure 'tis a shooe. ¹

A law of nature is a rule discovered by reason. ² This is the key to John Deigh's attempt to show that "Hobbes's ethics is logically independent of his moral psychology." ³ By this he means that the "theorems" of Hobbes's ethics, the laws of nature, "have no other ground than the definition on which it [his ethics] is based." ⁴ Deigh thinks he establishes this conclusion by taking seriously both Hobbes's definition of a law of nature as "a Precept, or generall Rule, found out by Reason, by which a man is forbidden to do, that, which is destructive of his life," and his definition of reason as "nothing but Reckoning (that is, Adding and Substracting) of the Consequences of generall names." ⁵ Deigh puts these two definitions together to argue that Hobbes's ethics is a deductive science, and that those who instead think of his ethics as dependent on desire or as involving instrumental reason ("means-to-ends thinking," as he calls it) are mistaken. The particular virtue of this interpretation, Deigh says, is that without it we have to read Hobbes in the Leviathan as sometimes using "reason" in a way that is different from the way he defines it in chapter 5. ⁶

I will argue that Deigh misunderstands the basis, status, and scope of Hobbesian natural law. In his attempt to save Hobbes from using "reason" equivocally, Deigh attributes mistakes and inconsistencies to him that are more serious and have less textual justification than that apparent equivocation. A source of the misunderstanding is a simplification—accepted by Mark Murphy and many other interpreters—of Hobbes's conception of reason.

Let us begin with Deigh's view of the scope of the law of nature, as he admits that his interpretation would be undermined were he wrong about this. "While the laws of nature are dictates of reason for people living in a state of nature," he says, "they are not truly laws in such circumstances and therefore not sources of obligation in them." ⁷ If Murphy is right that Hobbes does think they are obligatory outside of civil society, then it is, Deigh concedes, "a genuine problem" for his account. ⁸ In reply, Deigh refers to the two passages where Hobbes says that the laws of nature are "not properly Lawes," quoting the one from chapter 26, which explicitly recapitulates a claim from chapter 15. ⁹ In this earlier passage, however, Hobbes adds: "But yet if we consider the same Theoremes, as delivered in the word of God, that by right commandeth all things; then are they properly called Lawes." ¹⁰ Hobbes thinks that the laws of nature are always obligatory. He holds, for example, that the law of nature that covenants be kept obliges even "in the condition of meer Nature" or "condition of Warre," and that "the rule of Manners, without Civill Government, is the Law of Nature." ¹¹ Hobbes says that although the laws of nature donot always oblige "in foro externo; that is, to the putting them in act," they do always "oblige in foro interno; that is to say, they bind to a desire they should take place." ¹² Although they only require "a desire, and endeavour," Hobbes makes clear that these requirements are laws, and that they are binding and obligatory. ¹³

If Deigh were right, sovereigns would not be obligated by...