But in normal waking life this power of correction remains with us.

We may not exercise it, it is true, and thus the illusion will tend to become more or less persistent and recurring; for the same law applies to true and to false perception: repetition makes the process easier.

But if we only choose to exert ourselves, we can always keep our illusions in a nascent or imperfectly developed stage.

This applies not only to those half-illusions into which we voluntarily fall, but also to the more irresistible passive illusions, and those arising from an over-excited imagination.

Even persons subject to hallucinations, like Nicolai of Berlin, learn to recognize the unreal character of these phantasms.