It is not inhumane to keep a cat indoor-only. Cats are exposed to a variety of dangers, parasites, and diseases when allowed outdoors. Some hazards include: Fleas, Worms, Giardia, Coccidia, FIV, FeLV, Coyotes, Other Wildlife including cats & dogs, unkind humans, cars, and more. Cats can be incredibly happy living an indoor only life, especially if you provide them with plenty of enrichment. Create perches by the window ledges, use lots of toys, and provide 'hunt' type activities like the laser pointer! This will help ensure your kitty remains happy and healthy.
If you'd like to provide a safe outdoor space for your cat, consider an enclosed catio! Another great option for cats interested in exploring the outdoors; training them on a leash & harness! Always keep your kitty safe and either keep the indoors, or monitor their outdoor time. Do not leave them unattended to roam the streets.