Had there been no other personal attribute to influence the final outcome, Tarzan of the Apes, the young Lord Greystoke, would have died as he had lived — an unknown savage beast in equatorial Africa.
But there was that which had raised him far above his fellows of the jungle — that little spark which spells the whole vast difference between man and brute — Reason. This it was which saved him from death beneath the iron muscles and tearing fangs of Terkoz.

Ch. 12 : Man's Reason - Tarzan of the Apes (1912)