René Descartes' Second Meditation, from his Meditations on First Philosophy, is a pivotal moment in the development of his philosophical system. In this meditation, Descartes attempts to demonstrate the existence of the self and to establish the foundations for knowledge.
Descartes begins by doubting everything he can possibly doubt, including the existence of the external world and the reliability of his own senses. He then turns to the question of his own existence, stating that even if he were to doubt everything else, he must still exist in order to do the doubting. He famously declares, "I think, therefore I am" (Cogito, ergo sum in Latin), which has become known as the Cartesian Cogito.
Descartes then goes on to explore the nature of the self and its relationship to the body. He argues that the self, or the mind, is a distinct and separate entity from the body. This is because the mind is capable of thinking, while the body is not. The mind is also capable of understanding abstract concepts, such as mathematics, which the body is not.
Descartes also asserts that the mind is indivisible and indestructible. He argues that if the mind were divisible, then it would be composed of parts and would therefore be subject to change. However, the mind is capable of understanding itself, which suggests that it is a single, unchanging entity. Similarly, if the mind were destructible, then it would be subject to change and would therefore not be capable of understanding itself. Therefore, the mind must be indestructible.
In the Second Meditation, Descartes also introduces the concept of clear and distinct perception, which he sees as the basis for knowledge. He asserts that if an idea can be clearly and distinctly perceived, then it must be true. This is because the mind cannot perceive something clearly and distinctly unless it is actually present in the idea.
Overall, the Second Meditation is a crucial moment in Descartes' philosophical system, as it establishes the existence of the self and lays the foundations for knowledge. It has had a significant influence on subsequent philosophical thought and continues to be a subject of debate and discussion today.