inscrutable

This term describes a quality of opacity, often associated with a person's expression or a complex system that defies logical decoding. It suggests a deliberate or natural barrier that prevents an observer from discerning true intentions or meanings, creating a sense of detachment or mystery. While similar to mysterious, it specifically emphasizes the inability to be scrutinized or analyzed. It is frequently used in formal contexts to describe the "poker face" of a diplomat or the impenetrable nature of divine will or ancient laws.