§ 96 Corporeal Possession
Corporeal possession is clearly some form of continuing relation between a person and a material object. It is equally clear that it is a relation of fact and not one of right. It may be, and commonly is, a title of right; but it is not a right itself. A man may possess a thing in defiance of the law, no less than in accordance with it. Nor is this in any way inconsistent with the proposition, already considered by us, that possession may be such either in law or in fact. A thief has possession in law, although he has acquired it contrary to law. The law condemns his possession as wrongful, but at the same time recognises that it exists, and attributes to it most, if not all, of the ordinary consequences of possession.217
What, then, is the exact nature of that continuing de facto relation between a person and a thing, which is known as possession? The answer is apparently this: The possession of a material object is the continuing exercise of a claim to the exclusive use of it. It involves, therefore, two distinct elements, one of which is mental or subjective, the other physical or objective. The one consists in the intention of the possessor with respect to the thing possessed, while the other consists in the external facts in which this intention has realised, embodied, or fulfilled itself. These two constituent elements of possession were distinguished by the Roman lawyers as animus and corpus, and the expressions are conveniently retained by modern writers. The subjective element is called more particularly the animus possidendi, animus sibi habendi, or animus domini.
Apiscimur possessionem, so runs a celebrated sentence of the Roman lawyer Paul,218 corpore et animo, neque per se animo aut per se corpore. Neither of these is sufficient by itself. Possession begins only with their union, and lasts only until one or other of them disappears. No claim or animus, however strenuous or however rightful, will enable a man to acquire or retain possession, unless it is effectually realised or exercised in fact. No mere intent to appropriate a thing will amount to the possession of it. Conversely, the corpus without the animus is equally ineffective. No mere physical relation of person to thing has any significance in this respect, unless it is the outward form in which the needful animus or intent has fulfilled and realised itself. A man does not possess a field because he is walking about in it, unless he has the intent to exclude other persons from the use of it. I may be alone in a room with money that does not belong to me lying ready to my hand on the table. I have absolute physical power over this money; I can take it away with me if I please; but I have no possession of it, for I have no such purpose with respect to it.