[A*O]

Surely it depends on the cat's background. If it's been an indoor cat from birth and doesn't know any different than it's not a problem. But if you adopt an older stray that's used to being allowed to roam outside it's hardly fair to keep them cooped up indoors. We had a cat like that, adopted from the local animal rescue place and he was utterly miserable being an indoors cat. He used to pace up and down by the patio door mewing pathetically to be allowed out. We had to keep the house sealed up to stop him doing a runner. In the end we found him a new home with some friends who live in the country and as far as I know he's still there happily hunting rats. The happiest indoor cats I know have at least one other cat for company.