Most scholars of property law, at least in common law jurisdictions, subscribe to the view that there exists a rule of law that has the following content: when a person takes possession of land, or of a chattel, that person acquires a proprietary interest in relation to that land or that chattel. This interest is good against all those who do not have a stronger title, and those without a title stronger than that of the possessor will commit a legal wrong against her if they interfere with the land or chattel. Behind these propositions lie a number of puzzles. When will a person ‘take possession’ such that this proprietary interest arises? And why should we distribute unowned resources according to a rule of first possession, and not some other rule? In this book, Michael J.R. Crawford adds to the literature that examines these questions, and offers a theory of the rule that draws upon an impressively broad array of sources, ranging from the doctrinal to the game theoretical.

Before offering that theory, Crawford presents, in two introductory chapters, an admirably concise and clear restatement of the view that the basics of property law can best be understood by starting with the proposition that an owner of property is that person who has a right to exclude others from physically interfering with that property. Building out from that claim, Crawford argues that the role of possession in the law can be easily stated: the act of taking possession is one method – like others such as manufacture – by which one can acquire a right to exclude others from a particular item of property. Thus, possession is factual, and does not describe a right of any sort. It follows, on this account, that it is unhelpful to say that the property torts are concerned with interferences with possession. Suppose that I go on holiday and leave my bicycle unattended outside the front of my house. I can bring a claim in conversion against its thief. This is because I have a right to exclude others from the bicycle, and not because I ‘possess’ it despite being unable to touch, move, or physically prevent others from taking it (51).

With this framework in place, Crawford moves on to set out his theory of possession, which comes in two parts. The first examines the concept of ‘taking possession’ and asks what it means. He argues that many definitions of the concept – that focus on a person's control of a thing and on their intention in exercising that control – are wrong. Instead, a person will take possession of land or of a chattel wherever they perform an act that is, as a matter of social fact, an accepted way of signalling that person's intention to claim the land or chattel. Second, Crawford asks why possession has taken on its role as a method of creating property rights. His answer is that the law gives effect to a non-legal convention, that has, for reasons of human psychology, emerged as a salient way of resolving a coordination problem caused by the scarcity of resources. Possession (and its absence) is a very visible asymmetry that exists between two people in competition for a resource, and so the non-possessor spontaneously defers to the possessor's claim. Over time, a convention is created and, with it, norms which guide behaviour. It is in our interests to respect the convention, lest others take it upon themselves to challenge our own holdings.

Assessing theories of private law is a notoriously difficult task. Crawford's main aim is to promote understanding of the law as it is. He claims that the first limb of the theory ‘accurately describes the way in which possession works in the law’ in ways that other theories do not (64), and that the law's rules ‘cannot be understood’ in isolation from the second (113). Are either of these claims convincing? The first is hard to make out because Crawford does not offer a detailed account of alternative ‘theories’ of what it means to take possession. Clearly, the main competitor is one that defines possession as an appropriate degree of physical or factual control, paired with an intention to exercise that control on one's behalf. What it might mean to have such ‘control’ is not explicitly spelled out. Crawford primarily thinks of control as a factual ability to physically prevent other people from interfering with the land or chattel, but this is clearly not what the law requires. Nor is it impossible to think that ‘control’ might mean something very different: if I am steering a cruise ship, we can say that I control that ship, but I cannot hold it or physically prevent people from interfering with it, because of its size.

This lacuna leads Crawford into difficulty because he offers a theory of the law that appears to aim at replacing the law. It is the control-plus-intention test that courts actually apply to disputes, and it has the backing of a unanimous House of Lords (Pye v Graham [2002] UKHL 30). If our aim is to understand the law as it is, then we surely need very convincing reasons to suppose that the test does not accurately capture the law's substantive content. Without a detailed analysis of what the test might mean, and how those possible meanings map onto the case law, it is hard to see how a theory of the law can be justified in rejecting it.

On the second claim, it is not made entirely clear why we should accept that we cannot understand the law without Crawford's theory. Why do we need to know the cause of a legal rule if we are to understand its operation? It cannot be because we need that knowledge to iron out wrinkles in the law or to resolve novel cases. No matter how correct Crawford's theory of possession is, it cannot, without more, generate claims about how the law ought to deal with a given set of facts.

Seemingly aware of this point, Crawford offers, in addition to his theory, a normative defence of the law that is later used to resolve a number of well-known controversies. That defence is, again, composed of two elements. The first is the claim that the law is ‘minimally fair’ because ‘no one is systematically excluded from benefitting from it’ (132). Anyone can stake a claim to property by taking possession, and so no one is excluded from the rule on the basis of arbitrary personal characteristics such as their race or gender. The difficulty with this argument is that it seems to be wrong, in that it overlooks that some people, who are not able-bodied, may be excluded by a rule that requires them to perform physical acts. Crawford recognises this problem but is content to allow ‘redistributive mechanisms’ to correct this particular form of unfairness (134). Second, Crawford argues that the status of possession as a non-legal convention gives the law some good reasons to rely on it. In particular, he endorses the argument, most prominently made in a series of works by Thomas Merrill and Henry Smith, that law that is self-applying is likely to lead to minimal disputes and low administrative cost.

A reader new to property theory may wonder whether this is really the best that can be said in defence of the law. Crawford does not engage with the substantial literature that seeks to provide such a defence, but instead endorses the view that any such account is doomed to fail because it cannot get over the hurdle posed by the ‘unilateral’ element of acquisition: ‘as a general philosophical matter, it seems impossible to explain why any nominally duty-imposing act should bind others in the absence of their consent’ (123). This brief statement of the hurdle does not provide a full reflection of that philosophy. It has, for example, been argued – most prominently by Kant and his modern followers – that the problem could be dissolved through some legislative act of the state, or, alternatively, that the troubling features of a unilaterally imposed duty might be outweighed if the interests that the duty serves are sufficiently important. Although one might argue that neither of these responses is adequate to meet the unilateralism objection, it is a shame that Crawford does not consider them.

Given that Crawford's arguments provide only a relatively weak normative defence of the law, the prescriptive claims that he makes in the final few chapters are somewhat undermined. He considers three problematic areas: disputes between a finder of a lost chattel that is found on land occupied by someone who is not the owner of that chattel; the application of the law where the possessor in question is a thief; and the treatment of the good faith purchaser at common law. His argument in relation to the third can be the most easily stated: there is a conflict between the original owner and the purchaser because that purchaser has formed an expectation – on the basis of convention – that the seller of the property has an entitlement to it. There is therefore no good reason to favour one over the other, and we should be content with a certain rule that always favours original owners, or that always favours the bona fide purchaser (196).

The discussion of the other two problems is more interesting. Crawford argues that the rules governing lost chattels found on or under land should not be understood as being examples of the occupier of that land having possession of those chattels. Instead, ‘occupation of land’ lines up alongside manufacture and taking possession as one method by which one might acquire new rights in chattels (159). The reason for this is that a land occupier has no intention in relation to chattels lost by others on her land, and, Crawford argues, one cannot signal one's intention to claim a chattel if no such intention exists (66). Of course, it follows that the orthodox understanding of possession, as control plus intention, also straightforwardly suggests that these rules are not possessory.

Finally, Crawford endorses the view that a thief ought to acquire a proprietary interest in stolen property. He claims that, because people lack the information required to discern between innocent possessors and thieves, people will defer to a thief's possession regardless of the law's position (178). It is, however, hard to see how this can take the form of an argument about what the relevant legal rule ought to be. Crawford might be taken to be arguing that, if the law did not recognise title in the thief, it would not benefit from those values that a convention-based legal rule might be said to promote. If our focus is on minimising cost, plausibly the law's rules should be easy to follow, and one might think that citizens are more easily guided by norms of law that tell them not to interfere with possessed property, rather than norms that tell them not to interfere with innocently-possessed property. I doubt, however, that this argument works in this context. Those who deal with stolen property will owe duties in relation to that property to its true owner, and people will generally assume property that is possessed to have an owner. It follows that the norms imposed by the law in relation to a stolen chattel – even if the thief acquires no right that others not interfere with it – are perfectly clear and will be self-applied by citizens: do not interfere with it, because it is not yours.

Crawford's monograph is a welcome addition to the literature that examines personal property doctrine from a theoretical perspective. There is much to be gained from a close reading of his arguments, which cut across disciplines and should give as much food for thought to doctrinal lawyers as to legal theorists. If personal property scholarship is to make real progress, more work of this sort – that weaves doctrine and theory together – is sorely needed.

大多数财产法学者，至少在普通法司法管辖区，都同意这样一种观点，即存在具有以下内容的法律规则：当一个人占有土地或动产时，该人获得了以下内容的所有权权益与那块土地或动产的关系。这种利益对所有没有更强所有权的人都是有益的，而那些没有比占有者更强的所有权的人如果干涉土地或动产，就会对她犯下法律上的错误。这些命题的背后隐藏着许多谜团。一个人什么时候会“占有”从而产生这种专有利益？为什么我们要根据先占规则而不是其他规则分配无主资源？在这本书中，Michael JR Crawford 添加了研究这些问题的文献，

在提出该理论之前，克劳福德在介绍性的两章中以令人钦佩的简洁明了的方式重申了以下观点，即从财产所有人是有权获得财产的人这一命题开始，可以最好地理解财产法的基础知识排除他人对该财产的物理干扰。基于这一主张，克劳福德认为，占有在法律中的作用可以很容易地说明：占有行为是一种方法——就像制造等其他方法一样——通过这种方法，人们可以获得将他人排除在特定物品之外的权利的财产。因此，占有是事实，并不描述权利任何种类。因此，因此说财产侵权与对占有的干涉有关是无益的。假设我去度假，把我的自行车无人看管地放在我家门外。我可以对窃贼提出索赔。这是因为我有权将其他人排除在自行车之外，而不是因为我“拥有”它，尽管我无法触摸、移动或在身体上阻止他人使用它 (51)。

有了这个框架，克劳福德继续阐述他的占有理论，它分为两部分。第一个检查“占有”的概念并询问它的含义。他认为，这个概念的许多定义——侧重于一个人对事物的控制以及他们行使这种控制的意图——是错误的。取而代之的是，一个人在任何地方进行的行为都将占有土地或动产，作为社会事实，这是表明该人打算要求土地或动产的一种公认方式。其次，克劳福德问为什么占有作为一种创造财产权的方法发挥了作用。他的回答是，法律使一项非法律公约生效，由于人类心理的原因，成为解决因资源稀缺而导致的协调问题的一种突出方式。占有（及其缺席）是一种非常明显的不对称，存在于竞争资源的两个人之间，因此非占有者自发地服从占有者的主张。随着时间的推移，会产生一种惯例，并随之产生指导行为的规范。尊重公约符合我们的利益，以免其他人承担起挑战我们自己的责任。

评估私法理论是一项众所周知的艰巨任务。克劳福德的主要目的是促进对法律的理解。他声称该理论的第一部分以其他理论所没有的方式“准确地描述了占有在法律中的运作方式”（64），并且法律的规则与第二部分“无法理解”（113） ）。这些说法中的任何一个都令人信服吗？第一个很难弄明白，因为克劳福德没有提供关于占有意味着什么的替代“理论”的详细说明。显然，主要竞争者将占有定义为适当程度的身体或事实控制，同时意图代表自己行使这种控制。没有明确说明拥有这种“控制”可能意味着什么。Crawford 主要认为控制是一种实际能力，可以在身体上防止其他人干涉土地或动产，但这显然不是法律要求的。也不可能认为“控制”可能意味着非常不同的含义：如果我正在驾驶一艘游轮，我们可以说我控制了那艘船，但我无法控制它或在物理上阻止人们对其进行干扰，因为它尺寸。

这一缺陷导致克劳福德陷入了困境，因为他提供了一个理论的出现，瞄准替代法律的法律。这是法院实际适用于争议的控制加意图测试，它得到了上议院一致同意的支持（Pye v Graham [2002] UKHL 30）。如果我们的目标是按原样理解法律，那么我们肯定需要非常有说服力的理由来假设测试没有准确地捕捉到法律的实体内容。如果没有详细分析测试可能意味着什么，以及这些可能的含义如何映射到判例法，就很难看出法律理论如何能够证明拒绝它是合理的。

关于第二个主张，我们为什么要接受如果没有克劳福德的理论我们就无法理解法律，这一点并不完全清楚。如果我们要了解法律规则的运作，为什么我们需要知道法律规则的成因？不能因为我们需要这些知识来消除法律中的皱纹或解决新案件。无论克劳福德的占有理论多么正确，如果没有更多，它就不能产生关于法律应该如何处理一组给定事实的主张。

克劳福德似乎意识到了这一点，除了他的理论之外，还提供了对法律的规范性辩护，后来被用来解决一些众所周知的争议。同样，这种防御由两个要素组成。第一个是声称法律是“最低限度的公平”，因为“没有人被系统地排除在受益之外”（132）。任何人都可以通过占有来索取财产，因此任何人都不会因种族或性别等任意个人特征而被排除在规则之外。这个论点的困难在于它似乎是错误的，因为它忽略了一些身体不健全的人可能会被要求他们进行身体活动的规则排除在外。克劳福德承认这个问题，但满足于允许“再分配机制”来纠正这种特殊形式的不公平（134）。其次，克劳福德认为，占有作为一种非法律惯例的地位为法律提供了一些很好的理由来依赖它。他特别赞同托马斯·梅里尔 (Thomas Merrill) 和亨利·史密斯 (Henry Smith) 的一系列作品中最突出的论点，即自我适用的法律可能会导致最小的争议和低行政成本。

刚接触财产理论的读者可能想知道这是否真的是捍卫法律的最佳方式。克劳福德并未参与寻求提供此类辩护的大量文献，而是赞同这样一种观点，即任何此类帐户都注定要失败，因为它无法克服“单边”收购要素构成的障碍：“作为一般哲学问题，似乎无法解释为什么任何名义上的义务施加行为在未经他人同意的情况下应该约束他人”（123）。这个障碍的简短陈述并没有全面反映这种哲学。例如，有人认为——康德及其现代追随者最为突出——这个问题可以通过国家的一些立法行为来解决，或者，或者，如果义务所服务的利益足够重要，单方面施加的义务的令人不安的特征可能会被抵消。虽然有人可能会争辩说，这些回应都不足以满足单边主义的反对意见，但克劳福德没有考虑它们是一种耻辱。

鉴于克劳福德的论点仅提供了相对较弱的法律规范性辩护，他在最后几章中提出的规范性主张在某种程度上被削弱了。他考虑了三个有问题的领域：在非该动产所有人占用的土地上发现的丢失动产的发现者之间的纠纷；在有关占有人是小偷的情况下适用法律；以及善意购买者在普通法下的待遇。他关于第三点的论点可以最容易地表述出来：原始所有者和购买者之间存在冲突，因为购买者已经形成了一种期望——根据惯例——该财产的卖方有权获得该财产. 因此没有充分的理由偏爱一个而不是另一个，

另外两个问题的讨论更有趣。克劳福德辩称，管理在土地上或土地下发现的遗失动产的规则不应被理解为该土地的占用者拥有这些动产的例子。相反，“占领土地”与制造和占有并列，作为一种可以获得动产新权利的方法（159）。这样做的原因是，土地占有者对他人在其土地上失去的动产没有任何意图，而且，克劳福德认为，如果不存在这种意图，就不能表明自己有要求动产的意图（66）。当然，正统的对占有的理解，作为控制加意图，也直接表明这些规则不是占有。

最后，克劳福德赞同小偷应该获得被盗财产的所有权权益的观点。他声称，由于人们缺乏区分无辜拥有者和小偷所需的信息，因此无论法律的立场如何，人们都会服从小偷的拥有（178）。然而，很难看出这如何能够采取关于相关法律规则应该是什么的争论的形式。成为。克劳福德可能会被认为是在争辩说，如果法律不承认小偷的所有权，那么它就不会从基于公约的法律规则可能会促进的那些价值观中受益。如果我们的重点是最小化成本，那么法律规则似乎应该很容易遵循，并且人们可能会认为公民更容易受到告诉他们不要干涉拥有的财产的法律规范的指导，而不是告诉他们不要干涉的规范干涉无辜拥有的财产。然而，我怀疑这个论点在这种情况下是否有效。处理被盗财产的人将对该财产的真正所有者负有责任，人们通常会承担拥有的财产以拥有所有者。

克劳福德的专着是对从理论角度研究个人财产学说的文献的一个受欢迎的补充。仔细阅读他的论点可以收获很多，这些论点跨越学科，应该给理论律师和法律理论家一样多的思考。如果个人财产研究要取得真正的进展，则迫切需要更多此类将学说和理论编织在一起的工作。