6. The book of Isaiah naturally falls into two great divisions. The first, after an introductory chapter, contains a great variety of prophetic messages, delivered on special occasions. Chaps. 2-39. The second division, comprising the remaining twenty-seven chapters, seems to have had no special occasion, but to have been written after the overthrow of Sennacherib's army, probably in the old age of the prophet, for the comfort and encouragement of God's people in all coming ages. "Comfort ye, comfort ye my people, saith your God"--this is its great theme as expressed in the introductory verse. Of the various plans for _classifying the contents_ of the first part, all that rest upon the rationalistic view that the book is a collection of writings belonging to different authors and ages are false and groundless. Among evangelical men, who hold the unity of the book and its authorship by Isaiah, there have been various schemes of classification. It has been proposed by Drechsler and others to arrange all of Isaiah's prophecies around two great central events in the history of his times; namely, the invasion of Judah in the reign of Ahaz by the allied forces of Israel and Syria (chap. 7), and in Hezekiah's reign by Sennacherib, king of Assyria (chaps. 36, 37). That these were the two great crises of Isaiah's age, and that many of his prophecies had reference to them directly or indirectly, cannot be denied; but to affirm that _all_ his prophecies, extending over a period of from forty-eight to sixty-two years, were connected with those two events, either directly or by way of anticipation beforehand and natural sequence afterwards, is more than can be established by any probable arguments. We must be careful not to thrust upon the prophet a systematic arrangement beyond any that ever existed in his own consciousness. The following brief analysis will be sufficient for the general reader.