The only thing that matters is whether the story is a good one and whether the picture is a nice one.

There is a delightful old picture painted on a wall away off at Assisi, in Italy, which shows St.Francis preaching to a lot of birds, and the birds are all listening to him and looking pleased--the way birds do look pleased when they find a good fat worm or fresh crumbs.

Now, St.Francis was a real man and such a dear person too, but I don't suppose half the stories told about him were really true, yet we can pretend they were and that's just what the painter helps us to do.

Don't you know all the games that begin with 'Let's pretend' ?--well, that's art.

Art is pretending, or most of it is.
Pictures take us into a world of make-believe, a world of imagination, where everything is or should be in the right place and in the right light and of the right colour, where all the people are nicely dressed to match one another, and are not standing in one another's way, and not interrupting one another or forgetting to help play the game.
That's the difference between pictures and photographs.