Ninety percent of experienced, good cat guardians answering the question would probably agree with me to varying degrees. The answer depends on how long you intend to keep your cat in the basement and the reason for it. Another issue is whether the basement is safe for a cat for a short time. And I am writing on the basis that we are referring to a socialised domestic cat and a normal basement in a house.
I have made my point in referring to a ‘short time’. Without wishing to be rude, it would pointless to live with a cat if you intend to keep her in the basement the whole time. How is that living with a cat companion? Domestic cats are meant to be companions. That’s their primary role. How is your cat going to come up to you and jump onto your lap? How is she going to ask for a cuddle? She can’t unless for some strange reason you are living in the basement full-time.
It would also be cruel in my view. I remember a person keeping serval cats in their basement, a completely inappropriate decision. Some would say a mad decision.
If you are deciding to adopt a cat with the intention of keeping them in the basement full-time, please don’t adopt a cat. With the greatest of respect a person who wants to keep their domestic cat companion in the basement at all times is unsuited to be a cat owner. Cats need an enriched environment which is as natural as possible. A basement is the opposite to the desired objective: dark or dingy, potentially unsafe and sterile in terms of ambience. It is as far as can be from the sweet smelling outdoors of grass, vegetation, earth and trees. An enriched indoor environment with plenty of interaction can substitute the outdoors and it protects cats and wildlife. The best compromise is probably a cat of some sort or custom enclosure. A basement is at the far end of ‘no good’.
If you have a problem upstairs (e.g. building and decorating) which makes it unsafe for your cat companion and if the basement is safe for a cat i.e. no dangerous substances or cables etc. then it’s okay to put her down there for a short time by which I mean a day or two but no more. The basement should be throughly checked. Cats can get into mischief and trouble when left alone in such places. And they’d probably try to get out which can cause them harm.
And there should be frequent visits and interactions because it’ll be traumatic if the cat is used to having access to all parts of the home and light, space and nice smells. It’d would be dramatically more traumatic if she was an indoor/outdoor cat.
All in all not a good idea to keep a cat in a basement and, yes, I think that you’d find that most people would consider it cruel. I don’t think I am being too tough because if you don’t adopt a cat from a rescue center when you have the intention to put her in the basement that cat will probably be placed in a home where her life would be a lot better.