TREATISE ON MAN · Question 845

1Reply to Objection 2: The senses are suspended in the sleeper through certain evaporations and the escape of certain exhalations, as we read in De Somn. et Vigil. iii. And, therefore, according to the amount of such evaporation, the senses are more or less suspended. For when the amount is considerable, not only are the senses suspended, but also the imagination, so that there are no phantasms; thus does it happen, especially when a man falls asleep after eating and drinking copiously. If, however, the evaporation be somewhat less, phantasms appear, but distorted and without sequence; thus it happens in a case of fever. And if the evaporation be still more attenuated, the phantasms will have a certain sequence: thus especially does it happen towards the end of sleep in sober men and those who are gifted with a strong imagination. If the evaporation be very slight, not only does the imagination retain its freedom, but also the common sense is partly freed; so that sometimes while asleep a man may judge that what he sees is a dream, discerning, as it were, between things, and their images. Nevertheless, the common sense remains partly suspended; and therefore, although it discriminates some images from the reality, yet is it always deceived in some particular. Therefore, while man is asleep, according as sense and imagination are free, so is the judgment of his intellect unfettered, though not entirely. Consequently, if a man syllogizes while asleep, when he wakes up he invariably recognizes a flaw in some respect.