 The question of whether the deductively valid canonical syllogism spread from Dignāga to Praśastapāda, or from Praśastapāda to Dignāga, or from some other person to the two of them both has yet to be decided. Whatever the answer is to this question, it is clear that a deductively valid version of the canonical syllogism came to be adopted virtually by every classical Indian thinker and that it made its way to China, Korea and Japan through the spread of Buddhism.