ABSTRACT
Having announced his intention of attacking the foundations of his ‘present beliefs,’ Descartes proceeds:
All that I have up to now accepted as most true, I have received either from the senses or through the senses; these however I have sometimes found to deceive [fallere deprehendi], and it is prudent never to trust completely those which have once deceived us. (AT VII, 18; HR I, 145)
This truistic observation is followed by consideration of the much more significant proposal that the senses are reliable at least in circumstances that commonsense would regard as unproblematic:
But, although the senses sometimes deceive us about things that are very small and very distant, perhaps nevertheless there are many others about which it is completely impossible to doubt, although they are derived from the senses: such as that I am now here, seated by the fire, clothed in a winter robe, holding this paper in my hands, and similar things. For by what reason could the being of these hands themselves, and this whole body, be denied? [Manus vero has ipsas, totumque hoc corpus meum esse, quā ratione posset negari?] (Ibid.)
In calling into question this proposition Descartes considers first the fantasies of madness and then the experience of dreaming. In the condition of madness, he observes, people imagine they have an earthenware head, or are pumpkins, or are made of glass. However, this does not seem to him to provide a fully satisfactory ‘reason for doubt’ since ‘these people are insane and I would myself seem not less insane if I should transfer this case from them to myself’ (AT VII, 18-19; HR I, 145). At this point, however, the so-called Dreaming Argument is introduced as an acceptable reason for doubting these things. The phenomenon of dreaming can be used to make a point similar to that first attempted by the consideration of madness, without going outside the experiences of a normal person. Having noted that, as a man, he is accustomed to dream, Descartes continues:
How often indeed during repose at night am I persuaded of these familiar things, that I am here, clothed in a robe, seated near the fire, when I am nevertheless lying without clothes between the sheets! But now surely I view this paper with waking eyes, the head which I move is not somnolent, I extend and perceive this hand carefully and knowingly; things would not happen so distinctly to one asleep. As if I did not remember having been deceived on other occasions by similar thoughts in sleep; so that when I
think of this more attentively, I see so clearly that it is never possible to distinguish waking from sleeping by certain marks, that I am amazed, and this amazement almost confirms me in the supposition of sleep. (AT VII, 19; HR I, 145-6)
Descartes suggests, then, that the alleged impossibility of distinguishing waking from sleeping by certain marks provides some reason for doubting even those sense-based beliefs that concern the most obvious aspects of his current personal circumstances and surroundings.
