Rasiowa-Sikorski proof system for the non-Fregean sentential logic SCI ★

The non-Fregean logic SCI is obtained from the classical sentential calculus by adding a new identity connective = and axioms which say ‘a = ß' means ‘a is identical to ß'. We present complete and sound proof system for SCI in the style of Rasiowa-Sikorski. It provides a natural deduction-style method of reasoning for the non-Fregean sentential logic SCI.