Dogma
Dean supposes there have been a million religions before the ones we know today. He supposes some of them even had their own names for Cas. Well, maybe not him in particular... But his kind. Either malevolent or benevolent, somebody must've heard something. People always have their beliefs. Their systems. Their doctrines, that help them trudge through the sludge and misfortune of everyday life. That makes them hope that things are gonna stay good, once they get good. It's a basic need, religion.
Cas has his beliefs too. He's got his system. He struggles with it, but Dean knows that no matter where Castiel's loyalties lie on the field of battle, he's got his own structured principles that stand the undercurrent of his past mistakes and constant doubt. It's something that Dean can respect. He knws how hard it is to hold onto yourself when everything is flying apart in a cyclone around you.
Dean only has one system of belief, and it has three basic principles:
Family above all.
The good of all before what's good for himself.
Love and Castiel - mutually exclusive.
If he were asked outright what principles he lived by, he'd leave the third one out. That's just for him to know. But he'd say it in his head. Because as far as Dean can see, Castiel is the only thing worth praying to. He's the only solid belief that is consistent and reliable. Castiel is the primary basis Dean builds his entire ideology of love on.
He is a cautionary tale, a heroic journey, an unfinished story - imperfection and constant striving, beauty both lovely and terrible. Cas is a lot of things that make sense to Dean. He is, in a lot of ways, the epitome of what Dean believes.
And he wouldn't worship anything else.
