Human knowledge is like a circle. Inside the circle is known, and outside the circle is unknown. The more you know, the bigger the circle becomes, and the more you don’t know

——Zeno

Zeno is a famous philosopher in ancient Greece. Representative of the Eleatic faction, student and successor of Parmenides. Zeno is known as the "Father of Paradoxes". Four of his mathematical paradoxes have been passed down to this day. He once told a story about the "circle of knowledge". The story goes like this: Once, a student asked Zeno: "Teacher, your knowledge is many times more than mine, and your solution to the problem is very correct, but why do you always have questions about your answer?" Zeno drew two circles, one large and one small, on the table. He pointed at the two circles and said, "The area of ??the big circle is my knowledge, and the area of ??the small circle is your knowledge." The outside of these two circles is the ignorant part of you and me. The circumference of the big circle is longer than that of the small circle. Therefore, I am exposed to more areas of ignorance than you are. This is why I often doubt myself." In this story, Zeno compared knowledge to a circle, vividly revealing the dialectical relationship between knowledge and ignorance.