Which philosopher is known for the belief that certainty is unattainable?

The Sophists are recognized for their belief that certainty is unattainable, primarily because they emphasized the subjectivity of human knowledge and the relativity of truth. They argued that different individuals might have different perspectives and that what one person considers true may not hold for another, leading to the conclusion that absolute certainty in knowledge is impossible. This notion reflects their philosophical approach, which focused on rhetoric, debate, and the idea that knowledge can be constructed rather than discovered.

In contrast, the other philosophers mentioned, such as Plato, Democritus, and Aristotle, have various views about knowledge and reality, often suggesting frameworks where knowledge can be achieved, albeit through differing methods and systems of thought. For instance, Plato proposed the theory of forms, believing in a higher level of reality that could be known with certainty through philosophical reasoning.