Is it immoral to keep an animal as a pet, or is this question not within the

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Is it immoral to keep an animal as a pet, or is this question not within the domain of ethical philosophy? My reasoning is this, there are other much more self-involved things to do than spend time taking care of a pet, such as reading philosophy or even asking questions on this site. Pets can cause all kinds of problems, especially for its owner, and perhaps do not reciprocate affection.