This pretty thing is a Promethea Silk Moth (I think.) I found it on our hearth hidden behind some of Josie's books, and carried it outside, pausing to grab my camera.
How and when it got in, I do not know. The caterpillars are said to feed on apple trees, and we do have an apple tree just behind the house. It looked unharmed and I watched it flutter off. I hope it finds a mate.
For moths, like the worldview of a certain VP candidate, reproduction is everything.