We have spoken so far of ownership as something which explains itself, but in order to understand the next point it is necessary to enquire a little more closely into its nature. The Roman law of classical times is dominated by the absolute conception of ownership which it has evolved and by the action through which this right is asserted, the vindicatio. Ownership, in the developed law, may be defined as the unrestricted right of control over a physical thing, and whosoever has this right can claim the thing he owns wherever it is and no matter who possesses it.
If I possess a thing and you own it, then all you have to do is to prove your ownership and I must give it up; it is not necessary for you to allege that I have done you any wrong. I, on the other hand, the possessor, have nothing to do but to sit tight and wait for you to prove your right; if you do not succeed in proving that you are owner, I remain in possession. Now this very clear-cut conception is not to be found in all, or even most systems of law. English law, for instance, has never known an action corresponding to the vindicatio, at any rate with respect to movables. The action by which an owner recovers his thing which has got out of his possession all allege that the defendant "unjustly detains" the thing or that the plaintiff lost it, that it came into the hands of the defendant and that the defendant has converted it to his own use; to use technical language, the actions for the recovery of movables all "sound in tort". Further, the wrong alleged is, strictly, not one to ownership, but to possession, for, if the thing be "bailed", e.g. lent, by the owner to another, it is the bailee who can bring the action against the third party in whose hands the thing is found, the bailor being originally confined to his rights against the bailee. Hence it can be said that "although the bailor was the owner, the sum of his rights as owner was originally his better right as against the bailee to get possession; for this better right to get possession was the only form of ownership which the mediaeval common law recognised". This idea of a relative right to possession as contrasted with the absolute Roman dominium, is common to other Germanic systems of law besides the English, and it indeed appears that the Greeks also knew only of a similar relative right.
