I can't prove a mermaid exists because there is no evidence that suggests such, just as there is evidence for dogs, horses. So based on "evidence", I can say that horses dogs do exist. Note, this is based on "evidence" and not proof. Confusing yes, but what I am saying is that we all make our everyday judgements on what's real and not real based on evidence, not scientific proof. If I say I have a dog and show you my dog, no-ones going to ask me to prove it's a dog, evidence suggests it's a dog.
Very stupid argument but at the end of the day, people want "proof" of God, I say nothing can be proven, but we can look at the "evidence" and what does it point too?
I mean evidence suggests we are having this conversation, but still it can't be proven.