Tchaikovsky freely confessed later in life that he could not write within the proper rules of Western sonata form—those rules of exposition and organic growth and development of themes that Germanic composers such as Haydn and Mozart had invented. Anton Rubinstein was a slavish follower of those rules in his own works. That may in turn have been a handicap for Tchaikovsky in writing "Winter Dreams". He could not write a symphony that would please Rubinstein by staying firmly within a classical format while writing music that would stay true to his strengths as a composer.