Accordingly, it would be possible to state all cases of negligence in terms of imputed or presumed foresight.  It would be possible even to press the presumption further, applying the very inaccurate maxim, that every man is presumed to intend the natural consequences of his own acts; and this mode of expression will, in fact, be found to have been occasionally used, 1 more especially in the criminal law, where the notion of intent has a stronger foothold. 2 The latter fiction is more remote and less philosophical than the former; but, after all, both are equally fictions.  Negligence is not foresight, but precisely the want of it; and if foresight were presumed, the ground of the presumption, and therefore the essential element, would be the knowledge of facts which made foresight possible.

Taking knowledge, then, as the true starting-point, the next question is how to determine the circumstances necessary to be known in any given case in order to make a man liable for the consequences of his act.  They must be such as would have led a prudent man to perceive danger, although not necessarily to foresee the specific harm.  But this is a vague test.  How is it decided what those circumstances are?  The answer must be, by experience.

But there is one point which has been left ambiguous in the preceding Lecture and here, and which must be touched upon.  It has been assumed that conduct which [148] the man of ordinary intelligence would perceive to be dangerous under the circumstances, would be blameworthy if pursued by him.  It might not be so, however.  Suppose that, acting under the threats of twelve armed men, which put him in fear of his life, a man enters another’s close and takes a horse.  In such a case, he actually contemplates and chooses harm to another as the consequence of his act.  Yet the act is neither blameworthy nor punishable.  But it might be actionable, and Rolle, C. J. ruled that it was so in Gilbert v.  Stone. 1 If this be law, it goes the full length of deciding that it is enough if the defendant has had a chance to avoid inflicting the harm complained of.  And it may well be argued that, although he does wisely to ransom his life as he best may, there is no reason why he should be allowed to intentionally and permanently transfer his misfortunes to the shoulders of his neighbors.

It cannot be inferred, from the mere circumstance that certain conduct is made actionable, that therefore the law regards it as wrong, or seeks to prevent it.  Under our mill acts a man has to pay for flowing his neighbor’s lands, in the same way that he has to pay in trover for converting his neighbor’s goods.  Yet the law approves and encourages the flowing of lands for the erection of mills.