There is no way, other than to actually watch the artist make the art piece in front of you and with no trickery to make sure something is in fact the original.

There is no way, other than to actually watch the artist make the art piece in front of you and with no trickery to make sure something is in fact the original. When you realize that you'll understand why NFTs make no sense. Authentication is just the process of other people putting their reputation on the line to claim something is in fact what it claims to be; it is not absolute proof of anything. Authentication is not the word of god.