We have further to notice a =double= form of injustice which is specifically different from the simple kind, be it never so great. This variety may be detected by the fact that the amount of indignation shown by disinterested witnesses, which is always proportional to the amount of wrong inflicted, never reaches the =maximum= except when it is present. We then see how the deed is loathed, as something revolting and heinous, as an _ἄγος_ (_i.e._, abomination), before which, as it were, the gods veil their faces. =Double= injustice occurs when some one, after definitely undertaking the obligation of protecting his friend, master, client, etc., in a special way, not only is guilty of non-fulfilment of that duty (which of itself would be injurious to the other, and therefore a wrong); but when, in addition, he turns round, and attacks the man, and strikes at the very spot which he promised to guard. Instances are: the appointed watch, or guide, who becomes an assassin; the trusted caretaker, who becomes a thief; the guardian, who robs his ward of her property; the lawyer, who prevaricates; the judge, who is corruptible; the adviser, who deliberately gives some fatal counsel. All such conduct is known by the name of =treachery=, and is viewed with abhorrence by the whole world. Hence Dante puts traitors in the lowest circle of Hell, where Satan himself is found (_Inferno_: xi, 61-60). As we have here had occasion to mention the word "obligation," this is the place to determine the conception of =Duty=, which is so often spoken of both in Ethics and in real life, but with too wide an extension of meaning. We have seen that wrong always signifies injury done to another, whether it be in his person, his freedom, his property, or his honour. The consequence appears to be that every wrong must imply a positive aggression, and so a definite act. Only there are actions, the simple omission of which constitutes a wrong; and these are Duties. This is the true philosophic definition of the conception "Duty,"--a term which loses its characteristic note, and hence becomes valueless, if it is used (as hitherto it has been in Moral Science) to designate all praiseworthy conduct. It is forgotten that "Duty"[7] necessarily means a =debt= which is owing, being thus an action, by the simple omission of which another suffers harm, that is, a wrong comes about. Clearly in this case the injury only takes place through the person, who neglects the duty, having distinctly pledged or bound himself to it. Consequently all duties depend on an obligation which has been entered into. This, as a rule, takes the form of a definite, if sometimes tacit, agreement between two parties: as for instance, between prince and people, government and its servants, master and man, lawyer and client, physician and patient; in a word, between any and every one who undertakes to perform some task, and his employer in the widest sense of the word. Hence every duty involves a right;