Plato's later disciples, the Neo-Platonists, credit him with a secret doctrine which he imparted only to those who were worthy, and which he conveyed under the "seal of secrecy." His teaching was looked upon as mysterious in the same sense as the wisdom of the Mysteries. Even if the seventh Platonic letter is not from his hand, as is alleged, it does not signify for our present purpose, for it does not matter whether it was he or another who gave utterance to the view expressed in this letter. This view is of the essence of Plato's philosophy. In the letter we read as follows: "This much I may say about all those who have written or may hereafter write as if they knew the aim of my work,--that no credence is to be attached to their words, whether they obtained their information from me, or from others, or invented it themselves. I have written nothing on this subject, nor would anything be allowed to appear. This kind of thing cannot be expressed in words like other teaching, but needs a long study of the subject and a making oneself one with it. Then it is as though a spark leaped up and kindled a light in the soul which thereafter is able to keep itself alight." This utterance might only indicate the writer's powerlessness to express his meaning in words,--a mere personal weakness,--if the idea of the Mysteries were not to be found in them. The subject on which Plato had not written and would never write, must be something about which all writing would be futile. It must be a feeling, a sentiment, an experience, which is not gained by instantaneous communication, but by making oneself one with it, in heart and soul. The reference is to the inner education which Plato was able to give those he selected. For them, fire flashed forth from his words, for others, only thoughts. The manner of our approach to Plato's _Dialogues_ is not a matter of indifference. They will mean more or less to us, according to our spiritual condition. Much more passed from Plato to his disciples than the literal meaning of his words. The place where he taught his listeners thrilled in the atmosphere of the Mysteries. His words awoke overtones in higher regions, which vibrated with them, but these overtones needed the atmosphere of the Mysteries, or they died away without having been heard.