Unknowable/ʌnˈnəʊəbl/ Definition 1 of 3Pro Tip 1/3Philosophical Use Used in discussions about existence, life's big questions and philosophical theories. Philosophers debate whether true purpose is unknowable. Pro Tip 2/3Intellectual Humility Acknowledges the limits of human knowledge and understanding. Even the greatest scientists admit some aspects of physics are unknowable. Pro Tip 3/3Conveys Mystery Adds a sense of mystery when describing something beyond comprehension. The motives behind the artist's last painting are unknowable.