Among the things that separate Amos from his predecessors is the use of a literary channel for the dissemination of his teaching, which was of course primarily preaching. This in itself marks a great change. What was it that led the Prophet to write down the message which he had delivered? It may have been that there was a tendency towards literature at that particular period, but even before this the habit of keeping records must have commenced, while there is evidence of collections of poems or sagas, such as the Book of Jasher, or the Book of the Wars of the Lord, being in existence from a very early period. It is evident therefore that we need some particular occurrence to account for the adoption of literature as the vehicle of Prophecy. It has been suggested that the cause is to be sought initially in the rejection of the message of Amos by those to whom it was delivered: he was aware of the permanent application of the truths that he had delivered, and since his own times would not hearken he resolved to commit them to the verdict of posterity. The example once set, it was natural for the succeeding Prophets to wish to give something more than the fleeting character of the spoken word to teaching that was new and that had been rejected, and therefore to adopt this form (Isa. viii. 16 f.). Whatever the cause, we are thankful for the results. The channel chosen for the preservation of their messages was not purely literary; the form is not that of the essay, or thesis; it has not the studied elegance of poetry, yet it rises above prose, and rhythmic verse is found scattered throughout their writings. These reports of passionate oratory fall naturally into poetic form as the Prophet is carried away by his message. Especially do we find a very extensive use of symbolism, which has proved a trap into which the literalist has hastened to fall.