1) Incomprehensibility 2) Obscureness 3) Obscurity 4) Reconditeness 
• (n.) The quality of being abstruse; difficulty of apprehension.
Ab·struse'ness noun The quality of being abstruse; difficulty of apprehension. Boyle. 
abstruseness 1. The quality of being unclear or abstruse and hard to understand; obscureness. 2. Wisdom that is recondite (little known; obscure), abstruse, and profound; 'The university students were confused by the professor's abstruseness in his lectures.' 3. Difficult to comprehend.
reconditeness noun the quality of being unclear or abstruse and hard to understand