Trespass lies for unintentional, as well as for intended wrongs. Any wrongful and direct application of force is redressed by that action. It therefore affords a fair field for a discussion of the general principles of liability for unintentional wrongs at common law. For it can hardly be supposed that a man's responsibility for the consequences of his acts varies as the remedy happens to fall on one side or the other of the penumbra which separates trespass from the action on the case. And the greater part of the law of torts will be found under one or the other of those two heads. It might be hastily assumed that the action on the case [81] is founded on the defendant's negligence. But if that be so, the same doctrine must prevail in trespass. It might be assumed that trespass is founded on the defendant's having caused damage by his act, without regard to negligence. But if that be true, the law must apply the same criterion to other wrongs differing from trespass only in some technical point; as, for instance, that the property damaged was in the defendant's possession. Neither of the above assumptions, however, can be hastily permitted. It might very well be argued that the action on the case adopts the severe rule just suggested for trespass, except when the action is founded on a contract. Negligence, it might be said, had nothing to do with the common-law liability for a nuisance, and it might be added that, where negligence was a ground of liability, a special duty had to be founded in the defendant's super se assumpsit, or public calling. /1/ On the other hand, we shall see what can be said for the proposition, that even in trespass there must at least be negligence. But whichever argument prevails for the one form of action must prevail for the other. The discussion may therefore be shortened on its technical side, by confining it to trespass so far as may be practicable without excluding light to be got from other parts of the law. As has just been hinted, there are two theories of the common-law liability for unintentional harm. Both of them seem to receive the implied assent of popular textbooks, and neither of them is wanting in plausibility and the semblance of authority.