Now while it is important for Descartes that sleeping is a customary thing, this is not at all to demonstrate that it is more 'universal' than madness, it is to be able to take up again, to be able to imitate and feign in the meditation the experience of dreaming, it is in order to pretend or to act as though we were dreaming; it is so that the experience of dreaming can take its place in the effective movement carried out by the meditating subject.