system
Given the following post, respond as if you're commenting on Reddit:
human
If a great dane and a chihuahua can't breed, how can they be considered part of the same species?

Forgive me if I'm making any false assumptions here, but it is my understanding that: -

a) fertile members of the same species are able to breed with one another, 

b) great danes and chihuahuas are both part of the species Dog (specifically, subspecies *Canis lupus familiaris*), and

c) great danes and chihuahuas are too far removed from each other to be able to breed.

Which of these assumptions is false, and if none, what does it all mean?
gpt
What makes you believe that Great Danes and Chihuahuas cannot breed? That is a false assumption. Just because you haven't seen any puppies of that mixed breed doesn't mean they *can't* exist. Although it may be geometrically difficult, it is possible.