For Pete's sake, give him the reward. Hang a calendar in the bathroom and buy some stick-on stars. Tell him, every 15 to 30 minutes, it's time to get on the potty now, and when he does, he gets a star on the calendar even if he doesn't pee. Pretty soon he'll get it, and after a while the stars will lose their pull (but they'll have allure to him for a while). He'll get it. Either that, or if it's too much work, put him into pullups.