Such a general view is very hard to find.  The law did not begin with a theory.  It has never worked one out.  The point from which it started and that at which I shall [78] try to show that it has arrived, are on different planes.  In the progress from one to the other, it is to be expected that its course should not be straight and its direction not always visible.  All that can be done is to point out a tendency, and to justify it.  The tendency, which is our main concern, is a matter of fact to be gathered from the cases.  But the difficulty of showing it is much enhanced by the circumstance that, until lately, the substantive law has been approached only through the categories of the forms of action.  Discussions of legislative principle have been darkened by arguments on the limits between trespass and case, or on the scope of a general issue.  In place of a theory of tort, we have a theory of trespass.  And even within that narrower limit, precedents of the time of the assize and jurata have been applied without a thought of their connection with a long forgotten procedure.

Since the ancient forms of action have disappeared, a broader treatment of the subject ought to be possible.  Ignorance is the best of law reformers.  People are glad to discuss a question on general principles, when they have forgotten the special knowledge necessary for technical reasoning.  But the present willingness to generalize is founded on more than merely negative grounds.  The philosophical habit of the day, the frequency of legislation, and the ease with which the law may be changed to meet the opinions and wishes of the public, all make it natural and unavoidable that judges as well as others should openly discuss the legislative principles upon which their decisions must always rest in the end, and should base their judgments upon broad considerations of policy to which the traditions of the bench would hardly have tolerated a reference fifty years ago.

[79] The business of the law of torts is to fix the dividing lines between those cases in which a man is liable for harm which he has done, and those in which he is not.  But it cannot enable him to predict with certainty whether a given act under given circumstances will make him liable, because an act will rarely have that effect unless followed by damage, and for the most part, if not always, the consequences of an act are not known, but only guessed at as more or less probable.  All the rules that the law can lay down beforehand are rules for determining the conduct which will be followed by liability if it is followed by harm—­that is, the conduct which a man pursues at his peril.  The only guide for the future to be drawn from a decision against a defendant in an action of tort is that similar acts, under circumstances which cannot be distinguished except by the result from those of the defendant, are done at the peril of the actor; that if he escapes liability, it is simply because by good fortune no harm comes of his conduct in the particular event.