When you combine them, 天经地义 (tiānjīngdìyì) literally means “Heaven's principles and Earth's righteousness.” It beautifully merges the cosmic order (天经) with human morality (地义) to describe a truth that is both naturally and ethically absolute.
天经地义 is a concept deeply embedded in Chinese culture, drawing from both Confucian and Daoist thought. It reflects the belief in a harmonious order that governs the cosmos, nature, and human society. A core idea is that human actions should align with this universal order (the “Dao” or “Way”). To say something is 天经地义 is to claim it aligns with this fundamental order. Historically, this was used to justify social hierarchies and duties, such as filial piety (children's respect for parents) or a subject's loyalty to the ruler. Comparison to a Western Concept: A common English translation is “it goes without saying” or “as a matter of course.” However, these phrases lack the profound weight of 天经地义.
For example, saying “Paying for what you buy is 天经地义” is much stronger than “It goes without saying that you should pay.” The first suggests it's a pillar of a functioning, moral society; the second just states it's an obvious expectation.
In modern China, 天经地义 is still a common and powerful idiom. It's used to assert that a certain action or belief is undeniably correct.