Nothing is purely good or bad—duality explains why. Duality refers to the presence of two opposite but interconnected aspects within the same system, idea, or reality. It explains how contrasting forces—such as light and darkness, good and evil, success and failure, order and chaos—exist together and define each other. Without one side, the other loses its meaning. In philosophy, duality helps us understand that reality is not one-dimensional. Life is shaped by balance and contrast, where opposi