What Is Fancy?

SISTER. I am to write three lines, and you Three others that will rhyme. There-now I've done my task. BROTHER. Three stupid lines as e'er I knew. When you've the pen next time, Some question of me ask. SISTER. Then tell me, brother, and pray mind, Brother, you tell me true: What sort of thing is fancy? BROTHER. By all that I can ever find, 'Tis something that is very new, And what no dunces can see. SISTER. That is not half the way to tell What fancy is about; So pray now tell me more. BROTHER. Sister, I think 'twere quite as well That you should find it out; So think the matter o'er. SISTER. It's what comes in our heads when we Play at 'Let's-make-believe,' And when we play at 'Guessing.' BROTHER. And I have heard it said to be A talent often makes us grieve, And sometimes proves a blessing.