Reasons for Doubt
THE MEDITATOR begins his search for reasons for doubting his former opinions by considering his former opinion that what his senses tell him is true. Even a little reflection shows him that what his senses tell him is not always true: sometimes they deceive him, for example, when he is looking at things that are small or far away. So he revises his approving opinion about the reliability of his senses: he holds in effect that what his senses tell him in favorable circumstances is true. His examples are these: “that I am here, sitting by the fire, wearing a winter dressing-gown, holding this piece of paper in my hands, and so on” and “that these hands [and] this whole body are mine” (2:13; AT 7:18). It is not clear exactly what leads him to say that he has formed these opinions in favorable circumstances. They don't involve looking at things that are small or distant; they don't involve situations that create sensory illusions, like the differing media that make a half-submerged oar look bent; they don't involve expert identifications or discriminations, as when a gardener judges that what he holds in his hands is an Icelandic poppy.1 But it is hard to tell whether one or another of these features is supposed to define this class of opinions.
The meditator at first says that “doubt is quite impossible” (2:13; AT 7:18) when he considers what his senses tell him in favorable circumstances. But he goes on nonetheless to offer two reasons for doubting these opinions, first by comparing himself to a lunatic, and then by reflecting upon dreaming. After he raises the lunacy and dream considerations, the meditator asks himself whether any of his former opinions____________________