"Ode to a Grecian Urn" by John Keats
"Than ours, a friend to man, to whom thou say’st,
‘Beauty is truth, truth beauty’—that is all
Ye know on earth, and all ye need to know."
What you thought: If it looks good, it must be true. That's why we trust all the ads at Sephora.
But actually: Nobody is sure who is saying the last lines of this poem. Is Keats saying it to the urn? Or is the urn saying it to all of us? If Keats is telling the urn "that's all you need to know," it may actually mean that the urn only needs its truth = beauty math, but that that equation is not very helpful for the complications of real human life. So this may not be the sentimental aphorism we tend to read it as: it might actually just be Keats saying that it's easy to be a pretty vase, but being a person is much trickier.