aB rule Let a, c be wffs and y be individual variables. If 1.y is not free in c 2. y is free for in c 3.A Then Vxc Logic in Computer Science - p 9/27αβ Rule Let A, C be wffs and x, y be individual variables. If 1. y is not free in C 2. y is free for x in C 3. ` A Then ` A∀xC ∀ySxy C Logic in Computer Science – p.9/27