I think it's more an issue of how language and human brains work, than features of the world around us. The concepts behind words in human languages are extrem

I think it's more an issue of how language and human brains work, than features of the world around us. The concepts behind words in human languages are extremely fuzzy and ambiguous. That is why progress on computational linguistics was stuck for a long time, until researchers started using statistical models. This fuzzy and ambiguous way of modeling the world seems to better fit whatever it is our brains do. The definition of what is or isn't "life" is fuzzy and ambiguous, because however the concept is encoded in our brains is fuzzy and ambiguous.