to be repaid’.36 There are two ideas here. The first is that refraining from repairing the costs one imposes is just like destroying another’s property when merely using it would suffice. Each is an instance of taking more than one needs. The second is that what imposes the duty of repair is not the principle that one ought to depart from a default of a particularly robust interpretation of the right to exclude as little as possible, but, rather, that the right of necessity only permits one to take what one needs to extricate oneself from the perilous situation. To take more, indeed, would arguably violate natural equity because it in effect and at least in part would allow someone to arbitrarily determine how another’s property should be used, contrary to the independence at the heart of the sense of equality upheld by natural equity.37

4. Three Important Objections

Three important objections can be raised to this account.

1. The first questions its justificatory structure, that is, its accounting for what makes the adoption of private property possible and setting the conditions under which it is permissible by considering how we might move into such a regime from an original condition of common ownership. This might be thought to be objectionable on a number of grounds: that the original community of property is probably a fiction and in any case prehistoric; that even if it were a matter of historical record, nothing would come of it because facts don’t entail values; and that even if—indeed especially if—it is not meant to represent a period of history but is rather a kind of construct, it is justificatorily unhelpful because it builds the conclusion into the premisses. Finally, one might argue that the move from a world of unowned things to a world of property is not the right place to begin a theory of property, on the grounds either that a theory of property ought to begin with articulating the structure of ownership rather than its acquisition or that, because our world is a world in which all acquisition is derivative, if the structure of ownership can be explained by an analysis of acquisition it would not be original acquisition that would bear that normative weight.

The first step of the answer to these challenges is that they suppose that the idea of the original community bears a different sort of weight in Grotius’s account than it

36Grotius 1625, Bk. III, ch. 17, para. 1.1.

37James Penner raised the following important objection to this account of the duty to repair. If the guiding principle is that we depart from the regime of ownership as little as possible, it arguably follows that what necessity does, at most, is force sales. The point is most sharply made in a case where the defendant consumes rather than merely uses the plaintiff ’s property. (While holed up in his cabin during a storm, say, she eats some of the food she finds there.) Penner’s thought is that the owner’s title is better respected by compelling him to sell his property than it is by compelling him to make a gift of it; that the former marks a more modest departure from the regime of property. That seems right. But the objection takes as a starting point what Grotius denies, namely that the imperilled trespasser’s consumption of the food is an infringement (however well justified) of another’s property right. In a way I will elaborate in the conclusion, for Grotius the right of necessity is in a sense a property right, rather than a right that another allow one to use her property.

does. It is really a representation of a conception of equality, conjoined with some non-controversial facts. The non-controversial facts are that we cannot but occupy parts of the world and consume its resources. The normative work is done by the claim that until we choose to organize ourselves around a regime of private property, no one can by right exclude another from a part of the world she is not possessing. And this, in turn, is a claim about our equal standing with respect to our common world. This claim is not a claim about a period in history; nor, because it is not itself a claim about the structure or content of private property, does it smuggle the conclusion of Grotius’s argument into the premisses.

My suggestion is that the original community is a representation of these claims, as is, I would argue, the state of nature in early modern contract theories. For example, Hobbes’s account of the state of nature38 in the end comes down to the claim that we are equally vulnerable to one another and under no duty to defer to others’ judgments when we come into conflict. Similarly, the original position in Rawls’s theory of justice39 is a representation of a conception of equality, one that rests on a view about what is morally arbitrary from the point of view of distributive justice.

There is a second point of parallel with Hobbes and Rawls. Each takes the relevant position of equality as a baseline, departures from which need to be justified, and are justified only to the extent that they are necessary to realize the ends of the arrangement into which parties are represented as contemplating entering and only in terms acceptable from the perspective of the baseline. This structure is reflected in what Susanne Sreedhar calls ‘the necessity principle’ in Hobbes,40 and in what Rawls calls the difference principle. The necessity principle is the basis of what Hobbes calls the true rights of the subject, ‘those things, which though commanded by the sovereign, he may nevertheless, without injustice, refuse to do’.41 These rights are those that either we cannot give up or that it would be unnecessary to abandon to secure the benefits of the commonwealth.42 Rawls asks what departures from an equal distribution of basic material goods could be justified to those subject to an unequal distribution and concludes that it is only such inequality that would improve the condition of the worst off, and no more.43

What I called the foundational presumption in Grotius’s account has the same structure as the necessity and difference principles. The original community of property, the state of nature and the original position each represent the baseline in which the principles governing departures from them are anchored.

Finally, this explains why, prior to working out an account of the structure of property rights, and even in a world in which all acquisitions are derivative, it makes sense to ask on what terms we could move from a world of common ownership to a world of private property. That question just is a way to represent the question what the structure of property rights are, because it is a way to ask what structure is consistent with the normative constraints to which private property is subject.

41Hobbes 1651b, 21.10.

42‘Nor doth the law of nature command any divesting of other rights, than of those only which cannot be retained without the loss of peace’. Hobbes 1640, 93–4 (17.2).

43Rawls 1999, 55.

This is not Grotius’s express view. One might argue, however, that this is where his view ends up, if one begins by arguing that the sort of tacit, incremental consent that he claims accompanied the development of private property is not consent of the sort that does independent justificatory work. I won’t weigh in on this question here, except to note that we are on the edge of a basic question in political philosophy, namely whether actual consent to a set of political institutions is a necessary condition for their legitimacy, in particular for institutions that claim title to coerce or to authorize coercion. Answering yes leaves open the problem of the principled anarchist. The alternative is the claim that so long as that state does not deprive anyone of something to which they have a right, then no one has grounds on which to base principled resistance to or rejection of its authority. But this too seems unsatisfactory. It is one thing to say that I am not wronged by anyone whose actions are in conformity with what each of us is entitled to and another to say that anyone in particular, or any institution, has thereby been authorized to uphold those entitlements with force.

This doesn’t need to be settled here, where our interest is in the doctrine of necessity. But we might draw the lesson that, in this way, the theory of property invariably weighs in on a core issue in political philosophy.

3. The final objection concerns the foundational presumption. The worry is that it is indeterminate and—or perhaps ‘and therefore’—threatens to require the reshaping of a significant bit of property law and of doctrines in adjacent areas of private law that support the law of property (for example nuisance).

As with the second objection, there is a quick and arguably dispositive answer to this objection, but one that is admittedly unsatisfying. That answer is that this objection is strictly speaking not a worry here, where the claim is only that the foundational presumption yields the right of necessity. But of course if it does so at the expense of demanding an unacceptable revision of the laws of property and tort on pain of inconsistency then this response is too quick. So let’s dig more deeply.

A look back to Grotius will initially deepen but then, I will argue, answer the concern. What deepens the concern is Grotius’s argument that a second limit on the right to exclude is what he calls the Right of Harmless Use, the right that I may use another’s property if my use causes her no harm and if it is of benefit—in one formulation Grotius says great benefit—to me. Now he does not explicitly cast this right as an implication of the foundational presumption, but he does characterize it as sharing with the right of necessity two properties, namely that each is a nonconventional limit on private property and that we can suppose that the reservation of both was intended by those who introduced private property. And one might plausibly argue that the right of harmless use is entailed by the principle that in

we should understand the social contract in ‘On the common saying: that may be true in theory but is of no use in practice’. There Kant argues that the social contract is not a fact but rather ‘only an idea of reason, which, however, has undoubted practical reality, namely to bind every legislator to give his laws in such a way that they could have arisen from the united will of a whole people and to regard each subject . . . as if he has joined in voting for such a will’: Gregor ed. 1996, 296–7 (8: 297). One of the kinds of law to which a people could not have consented is one inconsistent with their legal equality.