Descartes’ Methodical Doubt: A Foundation for Certainty
Methodical Doubt
Descartes’ aim was to find absolutely certain truths, truths upon which it is impossible to doubt at all. These truths would provide a basis for building true knowledge with absolute security. The first problem was how to find them, and he developed a method to solve it. Once obtained, the question was where to start searching. The response, and the beginning of this process of finding true knowledge, is called methodical doubt.
The Process of Methodical Doubt
Requiring an absolutely true starting point necessitates a long process of criticism and elimination of all knowledge that had been considered true up to that point. However, this knowledge must not have absolute certainty that is beyond any possibility of doubt, which is very radical and extreme. The first step should be to doubt everything one believes and reject anything in which doubt is initially possible. The mere possibility of doubt will be sufficient grounds for rejecting an opinion or belief that we have considered true so far. It will remain in suspense until we see whether it conforms to the level of reason.
This first step will be called methodical doubt, the result of applying the first commandment of the method: “Never admit anything as true if I did not know it with evidence.” This certainty should not be considered real, but as a methodological tool to achieve its objective: to find a truth that can be the starting point of the edifice of knowledge. Descartes put forward three reasons for this doubt:
- Doubt about the reliability of the senses or concerns about the world of sense.
- The hypothesis of the dream, or the inability to distinguish waking from sleep.
- The hypothesis of the evil genius or hyperbolic doubt.
Doubt About the Reliability of the Senses
The senses bring us into contact with the material world and provide us with knowledge of things we usually accept as true. But we also know that sometimes, the senses deceive us.
Everything I’ve admitted to this day as safer and more true, I have learned from the senses or through the senses. However, I have experienced that sometimes these senses deceive me, and it is prudent never to trust entirely those who have ever deceived us.
There are a number of illusions and perceptual disturbances, such as when we see a stick immersed in water and it appears broken, yet we know that it is whole. Or when we see things affected by distance or other circumstances, as when we see a round tower from a distance and then discover that it is square. There are also hallucinations and other disturbances of perception that make us perceive as true or existing “realities” that are not at all. These facts are undeniable, but the extent of doubt is sufficient to discard sensory perception as a source of knowledge or to conclude from these experiences that the senses always deceive us.
The Dream Hypothesis: Inability to Distinguish Sleep from Wakefulness
Both when we are sleeping and when we are awake, we cannot distinguish between the two states. Sometimes we get the feeling that we can distinguish them because when we are asleep, dreams are less intense, as if being in a nebula. But when we have nightmares, the sensations intensify as if they were real. Moreover, considering that we have been deceived by the senses, who assures us that while we are reading this, we are not asleep? Because in some dreams, we dream as if we were in reality, before the fire, with paper in hand… Descartes concludes that we cannot distinguish sleep from wakefulness.