My now (almost) 8 year old was like this. He was 4.5 and was VERY stubborn in resisting potty use. No physical reason, he just didn't feel like it. No reward system worked. Being gross didn't phase him. We had to resort to A) making him clean up his mess (scrub floors, couches, dirty clothes etc) and B) Taking away piece by piece literally everything from him that he liked or could play with - since it was a "distraction" that made him not want to get up and go potty. He ended up spending his entire day for three days sitting on the bottom step of his grandma's stairway (since he was grounded from everything else, including TV), and that was enough for him. He finally got fed up with sitting there and never had another "accident" again. NOW, he was an extreme case for sure (the other 5, even when they fought me, were never so difficult to potty train) but I do think cleaning up, in addition to any other related "chores" you can think of is a great idea, and where a reward system won't work, explain to your son that it then becomes a "punishment" system, since he is a "big boy" like it or not (none of us get to go backward in time - you can't choose to be 4 and not have any of your mommy responsibilities - Daddy can't choose not to go to work), and there are some things that just have to happen when you are a big boy, like going on the potty. Explain that he needs to take care of his responsibilities as a big boy, even when he doesn't want to, or it becomes your job to find new ways to make him want to. Explain that while growing up brings new responsibilities, it also brings new rewards when we take care of our responsibilities (he can go to school once he's potty trained, and more of his friend's moms might be willing to have him over to play, etc) I agree with your husband that asking him may not be the best idea if he is being defiant, tell him you want him to go in and try. If he resists, tell him that when he refuses to make the decision when to get up and go potty, then it becomes your decision when he goes and how long he stays. Also, I LOVE the backpack idea. For us in the end it was extreme grounding that finally broke our son's resistance. Though it was really tough for us as parents to have to resort to that with a four year old. However, nothing else was working, and four and a half is pretty rediculous - when there is not a physiological reason for it.