The fact that other humans are so similar to me (all humans are similar in virtue of being human organisms) allows for an analogical inference: You guys are similar to me, I am conscious, therefore you are probably also conscious.
And whether or not something is conscious matters a lot ethically. If something is conscious, it may suffer. Conscious and unconscious objects have to be treated in a completely different way. We assume rocks aren't conscious and don't suffer from being broken apart, but we assume animals are conscious. That's why we treat them differently.
We can't know for certain whether something is or isn't conscious, but we have to try to make a best guess.
And whether or not something is conscious matters a lot ethically. If something is conscious, it may suffer. Conscious and unconscious objects have to be treated in a completely different way. We assume rocks aren't conscious and don't suffer from being broken apart, but we assume animals are conscious. That's why we treat them differently.
We can't know for certain whether something is or isn't conscious, but we have to try to make a best guess.