Mark Twain – Pessimism and optimism at 48 Share this quote: The man who is a pessimist before 48 knows too much; if he is an optimist after it, he knows too little. – Mark Twain (1835-1910) Is this quotation insightful, though-provoking, useful? Click on a star to rate it! Submit Rating Average rating 0 / 5. Vote count: 0