In order to lay the foundation of session as such, there must be detention, and there must also be the intention to or the " animus possidendi." the "animus possidendi" consists in the intention of exercising ownership. But this ownership may either be a person's own ownership, or that of another : if the latter, there is no such " animus possidendi " as makes de tention amount to possession. In the former case a man is a possessor, because he treats the thing as his own : it is not necessary that he should believe it to be his own.
Whether then we are considering pos session as such, or that possession which is concurrently acquired with ownership, or which completes the acquisition of, or is the exercise of, ownership, the material facts of possession are the same. When ownership is transferred from one man to another, every system of law must re quire some evidence of it. But the evidence of the transfer of ownership may be en tirely independent of the evidence of ac quisition of possession ; and also the evidence of the acquisition of possession may be inseparable from that of the ac quisition of ownership. There must then generally be some act which shall be evidence of the acquisition of possession, whether possession as such is obtained without ownership, or possession accom panied by ownership, or possession as necessary to the complete acquisition of ownership, or possession as simply the exercise of ownership.
It is remarked by Savigny (Das Becht des Besitzes, p. 185), in the whole theory of possession nothing seems easier to determine than the character of cor poreal apprehension which is necessary to the acquisition of possession. By this fact all writers have understood an im mediate touching of the corporeal thing, and have accordingly assumed that there are only two modes of apprehension : laying hold of a moveable thing with the hand; and entering with the foot on a piece of land. But as many cases occur in the Roman law in which posses sion is acquired by a corporeal act, with out such immediate contact, these cases have been viewed as symbolical acts, which, through the medium of juristical fiction, become the substitute for real ap prehension." After showing that this is not the way in which the acquisition of possession is understood in the Roman law, and that there is no symbolical ap prehension, but that the acquisition of possession may in all cases be referred to the same corporeal act, he determines what it is, in the following manner : " A man who holds a piece of gold in his hand is doubtless the possessor of it ; and from this and other similar cases has been abstracted the notion of a cor poreal contact generally as the essential thins in all acquisition of possession.
But in the case put, there is something else which is only accidentally united with this corporeal contact, namely, the physical possibility to operate imme diately on the thing, and to exclude all others from doing so. That both these things concur in the case put, cannot be denied : that they are only accidentally connected with corporeal contact, follows from this, that the possibility can be im magined without the contact, and the con tact without the possibility. As to the former case, he who can at any moment lay hold of a thing which lies before him, is doubtless as much uncontrolled master of it as if he actually had laid hold of it. As to the latter, he who is bound with cords has immediate contact with them, and yet one might rather affirm that he is possessed by than that he pos sesses them. This physical possibility then is that which as a tact must be con tained in all acquisition of possession : corporeal contact is not contained in that notion, and there is no case in which a fictitious apprehension need be as sumed." This clear exposition of a principle of Roman law is applicable to all sys tems of jurisprudence which have re ceived any careful elaboration, for the principle is in its nature general. It may be that the expounders of our law have not always clearly seen this prin ciple, even when they have recognised it; and it may be that they have not always acted upon it. Still it will ap pear from various cases that the physical possibility of operating on a thing is the es sential character of the acquisition of pos session in the English law. In the case of Ward v. Turner (2 Vez., 431) it was held by Lord Hardwioke that delivery of the thing was necessary in a case of " donatio mortis causi," and delivery of receipts for South Sea Annuities was not held sufficient to pass the ownership of the annuities. In his judgment Lord Hard wicke observed, " delivery of the key of bulky things, where wines, &c. are, has been allowed a delivery of the posses sion, because it is the way of coming at the possession, or to make use of the thing ; and therefore the key is not a symbol, which would not do." In one of his chapters (§ 16, Apprehension bewegli chen Sachen) Savigny uses the very same example of the key, showing that it is not a symbol, but the means of get ting at things which are locked up, and therefore the delivery of the key of such things, when they are sold, is a delivery of the possession. (See the cases in the Digest cited by Savigny, p. 209.)