what do I know?
(rhetorical question) Implies that a statement is based on a guess or assumption rather than on knowledge or evidence.
Maybe girl grasshoppers find long legs attractive in boy grasshoppers, but what do I know?
What do I know of man's destiny? I could tell you more about radishes. Samuel Beckett
What do I know of cultured ways, the gilt, the craft and the lie? I, who was born in a naked land and bred in the open sky. The subtle tongue, the sophist guile, they fail when the broadswords sing; Rush in and die, dogs-I was a man before I was a king. Robert E. Howard
What do I know about God and the purpose of life? I know that this world exists. Ludwig Wittgenstein
I write about sex, not love. What do I know about love? Sarah Jessica Parker
What do I know about sex? I'm a married man. Tom Clancy
We are as forlorn as children lost in the woods. When you stand in front of me and look at me, what do you know of the griefs that are in me and what do I know of yours? Franz Kafka