The climax of Charles Dickens wonderful classic A Christmas Carol comes when Scrooge, shaken by the scenes shown him by the Spirit of Christmas Yet to Come, pleads, "answer me one question. Are these the shadows of the things that Will be, or are they shadows of things that May be, only?" The ghost does not speak a word in answer to Scrooge.
And with good reason! For had the spirit responded, "These shadows are merely scenes of things that could be," Scrooge might well have breathed a sigh of relief and gone on with his life as before. "After all," he might quite rightly reflect, "almost anything could happen! No need to lose sleep about that!" On the other hand, if the spirit had told him candidly, "No, these shadows are not scenes to things that will be" (as we know to be true from the story's end), then Scrooge might have felt no cause for alarm at all, since none of what he had witnessed would in fact come to pass. In that case, he might not have been led to repent and change his life.
Scrooge's problem was that he was asking the wrong question; he had failed to exhaust the alternatives. For between what could be and what will be lies what would be. What the spirit was revealing to Scrooge was what would happen if Scrooge did not repent and change. The spirit was not exhibiting mere possibilities (it was possible that Scrooge would sell his business and open a flower stand and Covent Garden, but who cares about that? ), nor was he showing Scrooge what was in fact going to happen (Dickins assures us that Tiny Tim did not die). Rather the spirit was warning Scrooge that if he did not repent, all these terrible things would come to pass.
In philosophical terminology, the spirit was revealing to Scrooge a bit of counterfactual knowledge.
From The Middle-Knowledge View by William Lane Craig in Divine Foreknowledge: Four Views