Philipp Otto RungeThinkers

Black (n.) dirties ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠things, Runge said; if it only darkened it could be clear, but because it smirches it cannot be.