When we compare Zen as a finished product to the Doctrine of Enlightenment as the latter began to unfold itself in primitive Buddhism, we find a wide and seemingly impassable gap between the two. This was however naturally to be expected. Let us consider the following facts. In the beginning, the Buddha was somewhat timid to disclose the entire secrets of the reason of Buddhahood, thinking that his disciples were not quite capable of following every step he had taken himself. The feeling he first had after Enlightenment governed him almost throughout the entire course of his earthly life. It was this, that the Perfect Supreme Enlightenment attained by him was too exalted an object for sentient beings to strive after, and that even when it were disclosed to them they would not fully comprehend it but might defile it to their own demerit. Did he not even think of passing into Nirvana right after Enlightenment? His whole life, in spite of the advice of the Brahmadeva, seems to have been controlled by this feeling—the reluctance to reveal the entirety of his inmost self-realisation (_pratyātmajñāna_, according to the terminology of the _Laṅkāvatāra_). In point of fact, the Buddha himself might have communicated what he realised to all his disciples unreservedly, but the impression we get from the Agama or Nikaya literature is that he was actually reluctant to do so. At least this was the way the earlier writers of the canonical books attempted to represent their master whatever their motives might be. This being the case, the idea of Enlightenment was not brought forward so fully and conspicuously in Hinayana literature as at once to command our attention. But as I pointed out, this idea lies only superficially buried among the other and less important ideas, and can easily be made manifest by logically and psychologically following up the course of events related in the canonical writings concerning the Enlightenment of the Buddha.