empty theory; impractical theory
Refers to a theory or argument that is logically constructed but lacks practical applicability or real-world grounding. Often used in critical or dismissive contexts.
His proposal is nothing more than an empty theory.
That argument is just empty theory and impractical.
impractical theory; empty theory; academic discussion divorced from reality
Compound of 空 (くう, 'empty, void') and 理 (り, 'reason, principle'). The exact historical derivation is uncertain, but the word has been used in philosophical and critical discourse to denote theories lacking practical substance.