These fundamental criteria, it seems to me, can be reduced to the three following:--(1) No fixity in the periods of segregation of criminals; (2) the social and public character of the exaction of damages; (3) the adaptation of defensive measures to the various types of criminals. 1. For every crime which is committed, the problem of punishment ought no longer to consist in administering a particular dose, as being proportionate to the moral culpability of the criminal; but it should be limited to the question whether by the actual conditions (breach of law or infliction of injury) and by the personal conditions (the anthropological type of the criminal) it is necessary to separate the offender from his social environment for ever, or for a longer or shorter period, according as he is or is not regarded as capable of being restored to society, or whether it is sufficient to exact from him a strict reparation of the injury which he has inflicted. Under this head there is a radical contradiction. <p 208>The existing schemes of punishment, differing in their machinery (and out of harmony with the sentence of the judge, often even with the terms of the law), are all based on the principle of fixed periods of punishment, graduated into hundreds and thousands of possible doses, and have regard far more to the crime than to the criminal. On the other hand we have the positive system of punishment, based on the principle of an _unfixed segregation_ of the criminal, which is a logical consequence of the theory that punishment ought not to be the visitation of a crime by a retribution, but rather a defence of society adapted to the danger personified by the criminal. This principle of unfixed punishment is not new, but it is only the positive theory which has given it system and life. The idea of justice as assigning punishment to a crime, measured out by days and weeks, is too much opposed to the principle of the indeterminate sentence to allow it to receive any systematic trial under the sway of the classical theories. There has been only an isolated and exceptional use of it here and there, such as the seclusion of mad criminals in special asylums, ``during her Majesty's pleasure,'' in England. Nevertheless, personal freedom (which is held to be violated by seclusion for unfixed periods) is greatly respected by the English people. The fundamental principle of law is that of a restriction imposed by the necessity of social existence. It is evident, therefore, to begin with, that seclusion for an unfixed period, as for life, is in no way irreconcilable with this principle of law, when <p 209>imposed by necessity. Thus it has been proposed, even by the classical school, as a mode of compensation or adjustment.