Lyra and her dæmon moved through the darkening hall, taking care to keep to one side, out of sight of the… — Philip Pullman

"That light," said the Chaplain, "is it going up or coming down?"

"It's coming down," said Lord Asriel, "but it isn't light. It's Dust."

Something in the way he said it made Lyra imagine dust with a capital letter, as if this wasn't ordinary dust. The reaction of the Scholars confirmed her feeling, because Lord Asriel's words caused a sudden collective silence, followed by gasps of incredulity.

"But suppose your dæmon settles in a shape you don't like?"

"Well, then, you're discontented, en't you? There's plenty of fold as'd like to have a lion as a dæmon and they end up with a poodle. And till they learn to be satisfied with what they are, they're going to be fretful about it. Waste of feeling, that is."

Think of Adam and Eve like an imaginary number, like the square root of minus one: you can never see any concrete proof that it exists, but if you include it in your equations, you can calculate all manner of things that couldn’t be imagined without it.