The most certain foundation for the truth of confession in any case is the establishment of a clear motive for it--and that is rarely present. Of course the motive is not always absent because we do not immediately recognize it, but it is not enough to suppose that the confession does not occur without a reason. That supposition would be approximately true, but it need not be true. If a confession is to serve evidentially the motive must be clear and indubitable. Proof of its mere existence is insufficient; we must understand the confession in terms of all the factors that caused it. The process of discovering these factors is purely logical and generally established indirectly by means of an apagogue. This is essentially the proof by negation, but it may serve in connection with a disjunctive judgment which combines possible alternatives as a means of confirmation. We are, then, to bring together all conceivable motives and study the confession with regard to them. If all, or most of them, are shown to be impossible or insufficient, we have left only the judgment of one or more conclusions, and with this we have an essentially psychological problem. Such a problem is seldom simple and easy, and as there is no possibility of contradiction, the danger is nowhere so great of making light of the matter. “What is reasserted is half proved.” That is a comfortable assertion, and leads to considerable incorrectness. A confession is only established in truth when it is construed psychologically, when the whole inner life of the confessor and his external conditions are brought into relation with it, and the remaining motives established as at least possible. And this must be done to avoid the reproach of having condemned some confessor without evidence, for a confession having no motive may be untrue, and therefore not evidential. (b) _Partial confessions_ are difficult, not only because they make it harder to prove the evidence for what is not confessed, but also because what is confessed appears doubtful in the light of what is not. Even in the simplest cases where the reason for confession and silence seems to be clear, mistakes are possible. If, for example, a thief confesses to having stolen only what has been found in his possession but denies the rest, it is fairly probable that he hopes some gain from the evidence in which there appears to be no proof of his having stolen what has not been found upon him. But though this is generally the case, it might occur that the thief wants to assume the guilt of another person, and hence naturally can confess only to what he is accused of, inasmuch as he either has insufficient or no evidence whatever of his guilt for the rest of the crime.