Logician and philosopher recognized for An Essay in Modal Logic and Deontic Logic from 1951.
He received his formal education at the University of Helsinki. He became a noted authority on Ludwig Wittgenstein, the professor he succeeded at the University of Cambridge.
He received an honorary degree from the University of Bergen. He was an influential figure in philosophical logic, philosophical analysis, philosophy of action, philosophy of language, and philosophy of mind.
His family was residing in Helsinki when he was born.
He once taught at the University of Cambridge where Max Black studied philosophy.