Looked at from one (unreasonable) level, everything is unique. Looked at from another (unreasonable) level, most humans could be replaced with other humans and

Looked at from one (unreasonable) level, everything is unique. Looked at from another (unreasonable) level, most humans could be replaced with other humans and very little would change. There's no obvious-to-me level to look from where this argument applies to humans, but not to pet cats and dogs.