Although Bruce Lee is best known as a martial artist, he also studied drama and philosophy. He was well-read and had an extensive library. His own books on martial arts and fighting philosophy are known for their philosophical assertions both inside and outside of martial arts circles. His eclectic philosophy often mirrored his fighting beliefs, though he was quick to claim that his martial arts were solely a metaphor for such teachings. He believed that any knowledge ultimately led to self-knowledge, and said that his chosen method of self-expression was martial arts.