Speaking generally, the significant rule is this: _Egoism, laziness and conceit are the only human motives on which one may unconditionally depend_. Love, loyalty, honesty, religion and patriotism, though firm as a rock, may lapse and fall. A man might have been counted on for one of these qualities ten times with safety, and on the eleventh, he might collapse like a house of cards. Count on egoism and laziness a hundred or a thousand times and they are as firm as ever. More simply, count on egoism--for laziness and conceit are only modifications of egoism. The latter alone then should be the one human motive to keep in mind when dealing with men. There are cases enough when all the wheels are set in motion after a clue to the truth, i.e., when there is danger that the person under suspicion is innocent; appeals to honor, conscience, humanity and religion fail;--but run the complete gamut of self-love and the whole truth rings clear. Egoism is the best criterion of the presence of veracity. Suppose a coherent explanation has been painfully constructed. It is obvious that the correctness of the construction is studied with reference to the given motive. Now, if the links in the chain reach easily back to the motive, there is at least the possibility that the chain is free of error. What then of the motive? If it is noble--friendship, love, humaneness, loyalty, mercy--the constructed chain may be correct, and happily is so oftener than is thought; but it _need not_ be correct. If, however, the structure rests on egoism, in any of its innumerable forms, and if it is logically sound, then the whole case is explained utterly and reliably. The construction is indubitably correct. Section 8. (f) Secrets.