Luckily I've never had a cat with an opposable thumb (whew!). But where I live in california there is a highly permeable interface between indoor and outdoor,

Luckily I've never had a cat with an opposable thumb (whew!). But where I live in california there is a highly permeable interface between indoor and outdoor, with no screens. Most of the year there are doors and huge windows open all day unless nobody is home. In other words, I don't have a lifestyle that could feasibly restrict a cat to the indoors. When I lived on the 5th floor of a city building, yes. Other than that: no.