The characters combine literally to mean “to mix and muddle right and wrong.” The first two characters (混淆) create the action of “confusing,” while the last two (是非) define what is being confused: the fundamental concepts of truth and falsehood.
In Chinese culture, particularly influenced by Confucian thought, there is a strong emphasis on maintaining clear moral and social order. Concepts like justice (正义, zhèngyì) and distinguishing between good and evil are foundational. Therefore, the act of 混淆是非 is seen as a serious moral transgression. It's an attack on social harmony and clarity, an attempt to unravel the very fabric of ethical understanding. A useful Western comparison is the concept of “gaslighting” or “muddying the waters.”
To 混淆是非 is to reject the responsibility that comes with knowledge and power, using them instead to create chaos for personal gain.
This chengyu is formal but widely understood. It carries a strong, negative connotation and is used to make a serious accusation.