Let's look more closely at that episode of Professor Challenger. Apparently, what happened was that my agency for Work exploited Anger to stop Sleep. But why should Work use such a devious trick?
To see why we have to be so indirect, consider some alternatives. If Work could simply turn off Sleep, we'd quickly wear our bodies out. If Work could simply switch Anger on, we'd be fighting all the time. Directness is too dangerous. We'd die.
Extinction would be swift indeed for species that could simply switch off hunger or pain. Instead, there must be checks and balances. We'd never get through one full day if any agency could seize and hold control over all the rest. This must be why our agencies, in order to exploit each other's skills, have to discover such roundabout pathways. All direct connections must have been removed in the course of our evolution.
This must be one reason why we use fantasies: to provide the missing paths. You may not be able to make yourself angry simply by deciding to be angry, but you can still imagine objects or situations that make you angry. In the scenario about Professor Challenger, my agency Work exploited a particular memory to arouse my Anger's tendency to counter Sleep. This is typical of the tricks we use for self-control.
Most of our self-control methods proceed unconsciously, but we sometimes resort to conscious schemes in which we offer rewards to ourselves: If I can get this project done, I'll have more time for other things. However, it is not such a simple thing to be able to bribe yourself. To do it successfully, you have to discover which mental incentives will actually work on yourself. This means that you — or rather, your agencies — have to learn something about one another's dispositions. In this respect the schemes we use to influence ourselves don't seem to differ much from those we use to exploit other people — and, similarly, they often fail. When we try to induce ourselves to work by offering ourselves rewards, we don't always keep our bargains; we then proceed to raise the price or even to deceive ourselves, much as one person may try to conceal an unattractive aspect of a bargain from another person.
Human self-control is no simple skill, but an ever-growing world of expertise that reaches into everything we do. Why is it that, in the end, so few of our self-incentive tricks work well? Because, as we have seen, directness is too dangerous. If self-control were easy to obtain, we'd end up accomplishing nothing at all.