The oldest of our four cats, Patty, is declawed. I am not in favor of declawing, but as far as behavioural problems go, I don't think declawing has anything to do with making a cat more aggresive. Patty is our most well-adjusted cat, and is strictly indoors. She doesn't know she has no claws and uses the scratching post - and one of the chairs, just as the other cats do.