belly, and he begins clawing you vigorously with his back feet. (And yes, sometimes it hurts—and bleeds.) Don’t blame the cat.
Nature (meaning instinct) has taken hold, and the cat is protecting his most vulnerable spot, his belly. A cat has to learn to relax enough to let his belly be rubbed, and even in the most trusting of lap cats, the old instinct still tends to kick in (literally). Consider yourself lucky if your pet is so secure with you that you can stroke his belly with impunity.