I agree with you on the adult thing but one of my Mum's workmates was too scared to work through the gagging stage to get Amy to eat lumps and at 13 months she still required her food to be pureed. I'm positive Amy will learn to eat more solid food soon, but at the same time, all babies have to learn to get through their gagging reflex. If that is what is stopping your son eating lumps then keep trying and he'll get over it.
If it isn't that then keep going... it'll all happen eventually