You move into a new apartment or house, you have some furniture and you need to get some more, maybe sell or give away some that you brought with you. You start figuring out where it all goes: the sofa here, this lamp on that table. Should that wall have one big picture or several smaller ones? It can take a while and lots of trial and error before it feels right.
It feels right: that’s when it’s done. It’s no more scientific or even especially rational than that, yet the feeling of rightness can be as sure and settled as the conclusion of a syllogism. Feelings are facts.