On Dreams (Ancient Greek: Περὶ ἐνυπνίων; Latin: De insomniis) is one of the short treatises that make up Aristotle's Parva Naturalia.
[2] Finally, in the third chapter he explains how dreams are caused, proposing that it is the residual movements of the sensory organs that allow them to arise.
[5] He compares hallucinations to dreams, saying "...the faculty by which, in waking hours, we are subject to illusion when affected by disease, is identical with that which produces illusory effects in sleep.
[7] Ultimately, Aristotle concludes that dreaming is due to residual movements of the sensory organs.
This gives the reason why no dreams occur in sleep after meals, or to sleepers who are extremely young, e.g., to infants.