Beauty is truth–truth beauty–that is all ye know on earth and all ye need to know.
I don't agree with Keats that this is all ye need to know. But I do agree with the first part. Truth and Beauty are indeed an equality.
I learned this Beauty (Truth) in a college literature class c. 1984. In the context, our teacher was lecturing on children's fantasy literature. She asked the question, "is it OK to encourage children to read fantasy?" I already thought it was OK, having grown up loving all books. And, at the time of the lecture, I was deeply immersed in The Lord of the Rings universe, and had been for a couple of years. My professor made a powerful case that learning about myth - heroes, heroines, villains, and everymen - taught us about ourselves - truth.
But, what I DIDN'T understand about Truth and Beauty at the time was an even more powerful lesson. I have only recently learned it.
As a teenager and 20-something, I spent hours dreaming and drawing pictures and making plans for my perfect life. My plans always involved a rural homestead with animals and plants around me. Of course, my plans also involved riches and a huge house with beautiful decorations, so there's that :)
While I was planning, the life I was imagining felt then exactly like I feel today. My dreams came true, even though my naïve plans were pure fantasy. If I could find some of those notebooks with the plans and pictures, I would have a good laugh about naivete.
The Beauty that I imagined indeed turned into Truth that I now enjoy. And, they are one and the same.