First, to clarify. By inspiration, I do not mean that someone hears a voice telling them what to do. Instead, I mean the person has a vision of something higher, outside of themselves, that they try to replicate in their art. Maybe you already think this, and we're just talking past each other.

Homer starts off the Iliad with an invocation of the muse. Read Plato's dialogue Ion, where Socrates says exactly what I'm saying. Plus, you will find the same idea in Phaedrus, Republic, and the Symposium. I'm not saying Einstein is religious. He's obviously not a theist. But, he did think his ideas were not merely constructs out of his own mind but following some higher sense of beauty.

pg writes a similar idea in his essay on taste:

http://www.paulgraham.com/taste.html

He says taste is not subjective, not something people just create. There is a timeless logic to it.

Finally, in closing, here's a relevant cite from the very end of Dante's Paradiso:

As the geometrician, who endeavours

To square the circle, and discovers not,

By taking thought, the principle he wants,

Even such was I at that new apparition;

I wished to see how the image to the circle

Conformed itself, and how it there finds place;

But my own wings were not enough for this,

Had it not been that then my mind there smote

A flash of lightning, wherein came its wish.

Here vigour failed the lofty fantasy:

But now was turning my desire and will,

Even as a wheel that equally is moved,

The Love which moves the sun and the other stars.