1, the general suspicion in rene descartes.
In order to obtain absolutely certain knowledge, we must endlessly doubt, not only the existence of the sensory world, but also the illusory experience brought by sensory perception.
Even if it is a mathematical proposition that most of us believe, we should doubt it. Many people may think that whether asleep or awake, two plus three always equals five. Is it necessary to doubt such an obvious truth? No, Descartes said, these things still need to be doubted. Mathematics is the object of our thinking. However, all of a sudden, there may be annoying "ghosts" to confuse our spirit, put things that don't exist in our hearts and become the objects of our thoughts. Descartes said that this is not a joke or an alarmist. Just like the above three dreams, it is because of that "ghost" that I made a wrong judgment and mistook what I dreamed for reality.
2. rene descartes's skepticism
In the process of questioning all kinds of thinking objects, meditation subjects did not simply follow the logical exclusion idea of "gradually expanding the scope and gradually strengthening the utility", thus achieving the only remaining thinking fruit of "I think".
The real object of "doubt" is the Aristotelian cognitive principle, which has been popular for a long time in scholasticism and empirical science, that is, the "feeling principle", that is, "there is no knowledge without feeling imagination", which holds that sensory imagination is the source and foundation of all thoughts. In Descartes' view, this principle seriously affects the certainty of scientific knowledge. So Descartes' theory must take it as its main opponent. Before the metaphysical meditation, Descartes had determined his own path: he wanted to destroy the foundation of old knowledge-"feeling principle" by the method of "doubt". At the same time, I establish my own cognitive principle, that is, the "rational principle" derived from the self-evident of "I think", as a new foundation, and rebuild the building of deterministic knowledge on this basis.