The characters combine literally to mean “the wisdom (明) of (之) knowing (知) oneself (自)”. It’s a beautifully concise expression for a deep philosophical concept.
The concept of 自知之明 is deeply embedded in Chinese philosophy, originating from the foundational text of Daoism, the Tao Te Ching (道德经). The sage Laozi wrote: “知人者智,自知者明” (zhī rén zhě zhì, zì zhī zhě míng), which translates to: “He who knows others is intelligent; he who knows himself is enlightened (or truly wise).” This highlights a crucial distinction. While understanding others is a sign of intelligence (智), understanding yourself is a higher form of wisdom (明). This enlightenment isn't about knowing your passions or strengths, but about recognizing your limits, biases, and faults.
自知之明 is a common and powerful `chengyu` used across all registers of modern Chinese, from formal writing to everyday conversation.