According to Descartes, what is the only thing that could not be doubted?

René Descartes is famous for his philosophical statement “Cogito, ergo sum,” which translates to “I think, therefore I am.” This principle underlines the notion that the act of doubting or thinking itself is indubitable. In his method of radical doubt, Descartes sought to find a foundational belief that could not be questioned.

If he could doubt everything else — the existence of the physical world, his own body, and even the existence of other minds — he could not doubt the fact that he was doubting. The experience of doubt itself serves as proof of his own existence as a thinking being. Thus, the ability to doubt confirms that he exists as a conscious entity. This process illustrates Descartes' focus on the significance of thought and self-awareness in establishing certainty.

The other choices represent aspects that Descartes could conceive of doubt concerning. For example, while he may perceive the external world, those perceptions can be misleading, leading to doubt about their accuracy. Similarly, the existence of other minds is something Descartes considered possible to doubt, as it relies on evidence that is inherently subjective. Therefore, the correct understanding acknowledges that the only thing Descartes could not doubt is his own ability to