absent, he will be what he was before. The coercion must be an internal one, which he shall carry with him out of prison. It avails little that you force him to work; he must force himself to work. And this he will do, only when placed in those conditions which equity dictates. Here, then, we find a third order of evidences. Psychology supports our conclusion. The various experiments above detailed, carried out by men who had no political or ethical theories to propagate, have established facts which we find to be quite concordant, not only with the deductions of absolute morality, but also with the deductions of mental science. Such a combination of different kinds of proof, cannot, we think, be resisted. * * * * * And now let us try whether, by pursuing somewhat further the method thus far followed, we can see our way to the development of certain improved systems which are coming into use. Equity requires that the restraint of the criminal shall be as great as is needful for the safety of society; but not greater. In respect to the _quality_ of the restraint, there is little difficulty in interpreting this requirement; but there is considerable difficulty in deciding on the _duration_ of the restraint. No obvious mode presents itself of finding out how long a transgressor must be held in legal bondage, to insure society against further injury from him. A longer period than is necessary, implies an actual injustice to {181} the offender. A shorter period than is necessary, implies a potential injustice to society. And yet, without good guidance, one or other of these extremes is almost sure to be fallen into.