Maintaining waking consciousness seems to entail an energetic cost as if the brain machinery involved in the coordinated tasks that underlie this state becomes fatigued and needs to be refreshed in sleep. This is why the higher faculties of memory and reasoning become blurred and less and less available as the hours go by unless artificially boosted by stimulants, and sleep is felt to be a recharging of reservoirs of energy. Dreams might contribute to this by sorting and consolidating memories and emptying the buffers in which they are stored over short durations. In fact, to the degree to which our dreams are particularly energetic we might find that we wake up more tired in some respects than when we went to bed. The anomaly in this intuitive picture is the way that after a lucid dream one generally wakes far more refreshed and energised than after ordinary non-lucid dreaming. This in spite of the fact that some of the higher powers associated with wakefulness have been activated and put to work during lucid dreaming. This suggests that there is something about waking consciousness that is not simply the activation of machinery of wakefulness that is what is tiring. It is rather the constraint on consciousness in the waking state that is tiring, its being forced away from its native state. Just like the body having to turn about during sleep because nerves are squeezed and blood flow is restricted by remaining too long in one position, the consciousness in the ordinary waking state grows numb in parts because of the unnaturalness of its postures. What we think we know of consciousness is mediated by the parameters of waking consciousness, but these may be highly misleading due to their service of a body in an evolutionary landscape.