Question: are you a mouse or a man?
Answer: A man or a mouse is a proverbial expression to express risk or encourage a person to be daring. The idea is 'Be a man, or else don't pretend to be one but admit that you have what Chaucer's Pandarus [in Troilus and Criseyde (by 1386)] calls "a mouse's heart."' See [The] Schole-House of Women [1541/1572], 385 ff.