Eminent judges have been puzzled where to draw the line, or even to state the principle on which it should be drawn, between the two sets of cases. But the principle is believed to be similar to that on which all other lines are drawn by the law. Public policy, that is to say, legislative considerations, are at the bottom of the matter; the considerations being, in this case, the nearness of the danger, the greatness of the harm, and the degree of apprehension felt. When a man buys matches to fire a haystack, or starts on a journey meaning to murder at the end of it, there is still a considerable chance that he will [69] change his mind before he comes to the point. But when he has struck the match, or cocked and aimed the pistol, there is very little chance that he will not persist to the end, and the danger becomes so great that the law steps in. With an object which could not be used innocently, the point of intervention might be put further back, as in the case of the purchase of a die for coining. The degree of apprehension may affect the decision, as well as the degree of probability that the crime will be accomplished. No doubt the fears peculiar to a slaveowning community had their share in the conviction which has just been mentioned. There is one doubtful point which should not be passed over. It has been thought that to shoot at a block of wood thinking it to be a man is not an attempt to murder, /1/ and that to put a hand into an empty pocket, intending to pick it, is not an attempt to commit larceny, although on the latter question there is a difference of opinion. /2/ The reason given is, that an act which could not have effected the crime if the actor had been allowed to follow it up to all results to which in the nature of things it could have led, cannot be an attempt to commit that crime when interrupted. At some point or other, of course, the law must adopt this conclusion, unless it goes on the theory of retribution for guilt, and not of prevention of harm.