Greatness means the construction of an inner world, and the communication of this inner world to the physical world of humanity.  The two belong together; neither is thinkable without the other.  The strongest feeling and the most vivid imagination are worthless to humanity if they do not manifest themselves; the greatest constructive talent is worthless if it does not serve a creative power that is capable of forming a cosmos.

Einstein, Alfred (1941) Greatness in music.  Trans. César Saerchinger.  New York: Oxford, p.163.  Cited in: Barrett-Ayres, Reginald (1974) Joseph Haydn and the String Quartet.  London: Barrie & Jenkins, p. 387.