In Discipline and Punish, Foucault writes about the “temporal modulation” of punishment. This means that punishment should have a beginning and end; it should not go on forever like eternal damnation.
The penalty transforms, modifies, establishes signs, arranges obstacles. What use would it be if it had to be permanent? A penalty that had no end would be contradictory: all the constraints that is imposes on the convict and of which, having become virtuous once more, he would never be able to take advantage, would be little better than torture; and the effort made to reform him would be so much trouble and expense lost by society. If incorrigibles there be, one must be determined to eliminate them. But for all others , punishment can function only if it comes to an end. This analysis was accepted by the Constituent Assembly: the code of 1791 lays down the death penalty for traitors and murderers; all other penalties must have an end (the maximum is twenty years).p. 107
The beginning and end of punishment is a two-sided form. It is a binary distinction, excluding a third value. As Luhmann puts it,
A code consists of two opposing values, and [. . .] excludes a third and further values. This converts the possibility—indefinite but tending to increase—of the communicated meaning proposal being rejected into a hard either/or, that is, transforms an ‘analog’ situation into a ‘digital’ one.(2012, p. 215).
The advantage of a digital code is that there is no third, fourth, or n-value. There are just two values, both of which must be available or realizable, much like the two sides of a coin.
The boundary between the positive and negative side of the form must be crossable. In our example, this means that the penalty must end at some point. The two sides of the form can be considered horizons, which may be approached must but never reached or crossed. So the boundary between the sides must be crossable, but the horizons are not crossable. A horizon keeps receding as we approach it, and at some point we must turn back toward the other horizon.
In terms of the moral reform, becoming “virtuous once more,” that prison reform set out to achieve, virtue and vice are also horizons. One can never reach either horizon, which means that total virtue and total vice are equally unattainable. It must, of course, be possible to turn from vice to virtue. But it must also be equally possible to turn from virtue to vice. This means that human beings cannot be completely good or evil, saints or sinners.
Temporal modulation, of course, brings in the temporal dimension, or te past/future distinction. The convict has a past and a future, and the punishment has a beginning and end. The main difference between this kind of penalty and corporal punishment is that “modern” penal punishment is measured in the length rather than severity or brutality of the punishment. It not the body that suffers but the mind, as the convict contemplates the duration of his punishment, enduring the same indignities (lack of privacy, lack of freedom) day after day.