The objection may be urged, to be sure, that there is a considerable step from holding a man liable for the consequences of his acts which he might have prevented, to making him answerable for not having interfered with the course of nature when he neither set it in motion nor opened the door for it to do harm, and that there is just that difference between making a hole in a roof and leaving it open, or cutting the cord and letting it bleed, on the one side, and the case of a farrier who receives a sick horse and omits proper precautions, on the other. /1/ There seem to be two answers to this. First, it is not clear that such a distinction was adverted to by the court which decided the case which I have mentioned. It was alleged that the defendant performed his cure so negligently that the horse died. It might not have occurred to [280] the judges that the defendant's conduct possibly went no further than the omission of a series of beneficial measures. It was probably assumed to have consisted of a combination of acts and neglects, which taken as a whole amounted to an improper dealing with the thing. In the next place, it is doubtful whether the distinction is a sound one on practical grounds. It may well be that, so long as one allows a trust to be reposed in him, he is bound to use such precautions as are known to him, although he has made no contract, and is at liberty to renounce the trust in any reasonable manner. This view derives some support from the issue on which the parties went to trial, which was that the defendant performed the cure as well as he knew how, without this, that the horse died for default of his care (cure?). /1/ But it cannot be denied that the allegation of an undertaking conveyed the idea of a promise, as well as that of an entering upon the business in hand. Indeed, the latter element is sufficiently conveyed, perhaps, without it. It may be asked, therefore, whether the promise did not count for something in raising a duty to act. So far as this involves the consequence that the action was in fact for the breach of a contract, the answer has been given already, and is sustained by too great a weight of authority to be doubted. /2/ To bind the defendant by a contract, an instrument under seal was essential. As has been shown, already, even the ancient sphere of debt had been limited by this requirement, and in the time of Edward III. a deed was necessary even to bind a surety. It was so [281] a fortiori to introduce a liability upon promises not enforced by the ancient law. Nevertheless, the suggestion was made at an early date, that an action on the case for damage by negligence, that is, by an omission of proper precautions, alleging an undertaking by way of inducement, was in fact an action of contract.