The Book of Isaiah, the third longest book in the Bible after Psalms and Jeremiah, deals with as broad a range of theology as any book in the Old Testament. In this respect it is similar to Romans. However, there are four primary doctrines, all arising out of the prophet's personal experience with God in his call (ch. 6), that receive the most emphasis. These are God, man and the world, sin, and redemption.
Isaiah presented God as great, transcendently separate, authoritative, omnipotent, majestic, holy, and morally and ethically perfect. In contrast, he described sarcastically the stupidity of idolatry. God creates history as well as the cosmos, and He has a special relationship with Israel among the nations. The adjective "holy"(Heb. qadosh) describes God 33 times in Isaiah and only 26 times in the rest of the Old Testament. It is the primary attribute of God that this prophet stressed.
Isaiah showed the tremendous value that God places on humanity and the world but also the folly of pride and unbelief. Assuming pretensions to significance leads to insignificance for the creation, but giving true significance to God results in glory for humanity and the world. As all the other eighth-century prophets, Isaiah condemned injustice.
Sin is rebellion for Isaiah that springs from pride. The book begins and ends on this note (1:2; 66:24). All the evil in the world results from man's refusal to accept Yahweh's lordship. The prophet repeatedly showed how foolish such rebellion is. It not only affects man himself but also his environment. God's response to sin is judgment if people continue to rebel against Him, but He responds with redemption if they abandon self-trust and depend on Him. Sin calls for repentance, and forgiveness for the penitent is available.
God's judgment, the outworking of the personal rage of offended deity, takes many forms: natural disaster, military defeat, and disease being a few, but they all come from God's hand ultimately. The means of salvation can only be through God's activity. Substitutionary atonement makes possible God's announcement of pardon and redemption. This redemption comes through the promised Messiah ultimately, the Lord's anointed king. The goal of redemption is not just deliverance from sin's guilt but the sharing of God's character and fellowship. Salvation could only come to God's people as they accepted the role of servant. Deliverance cannot come to man through his own effort, but he must look to God alone for it. His emphasis on salvation has earned Isaiah the title of evangelist of the Old Testament.
Isaiah is strongly eschatological. In many passages the prophet dealt with the future destiny of Israel and the Gentiles. He wrote more than any other prophet of the great kingdom into which the Israelites would enter under Messiah's rule.
"We stand precisely on 56:1, looking back to the work of the Servant (now fulfilled in the person, life, death and resurrection of the Lord Jesus) and looking forward to the coming of the Anointed Conqueror."15
Isaiah's emphasis on the coming Messiah is second only to the Psalms in the Old Testament in terms of its fullness and variety. God revealed more about the coming Messiah to Isaiah than He did to any other Old Testament character. Messianic themes in Isaiah include the branch, the stone (refuge), light, child, king, and especially servant. In some of the passages in Isaiah, Israel is the servant of the Lord that is in view, in others the faithful remnant in Israel is the servant, and in still others a future individual, the Messiah, must be in view. As Matthew clarified, Jesus Christ was the fulfillment of what God intended the Israelites to be (Matt. 2:15; cf. Hos. 11:1-2).
"What is the overarching theme of OT theology? Perhaps it is the covenant. Here in Isaiah, God's special relationship with Israel is presupposed throughout. Perhaps it is the kingdom of God. The whole structure of the book brings out the implications of God's sovereign control of things in the interests of his kingdom. Perhaps it is promise and fulfillment. Here we see time and again the word of divine authority being fulfilled and further fulfillment thereby pledged. Perhaps it is simply God himself, Israel's Holy One. This book is one long exposition of the implications--for Israel and the world--of who and what he is. So this great prophecy--its whole structure unified by its teaching about the Holy One of Israel, who is true to his word, faithful to his covenant, and pursues the establishment of his kingdom--is a classic disclosure of the very heart of the OT faith."16
"The theological message of the book may be summarized as follows: The Lord will fulfill His ideal for Israel by purifying His people through judgment and then restoring them to a renewed covenantal relationship. He will establish Jerusalem (Zion) as the center of His worldwide kingdom and reconcile once hostile nations to Himself."17
