Particles of raw inspiration sleet through the universe all the time. Every once in a while one of them hits a receptive mind, which then invents DNA or the flute sonata form or a way of making light bulbs wear out in half the time. But most of them miss. Most people go through their lives without being hit by even one.
Not for the first time in the history of the universe, someone for whom communication normally came as effortlessly as a dream was stuck for inspiration when faced with a few lines on the back of a card.