He didn't believe me when I told him he was four. He thought something profound would happen, like he would suddenly shoot up an extra two inches or something. He looked confused and asked me, 'How come you can't see peoples grow?'. It took him a while to get his head around it. The fact that one day you are three and the next you are four and nothing much happens. You don't feel older, you don't look older but somehow you are. Just like that.