I was told in an Old Testament class that Isaiah was written by two authors. Is this true and if it is does that change the validity of the prophecies in the book?

Also, I have always believed that the gospels were found in different places but were in harmony. Is this true or what were the origins of the gospels?

I am a Christian but have been beating myself up trying to find answers to all of these questions I have.

Thanks for writing Probe Ministries. It is a very common view among moderate to liberal biblical scholars that Isaiah had two authors. Indeed, some even believe that there were three (or more) authors of this book. A disbelief in the validity of predictive prophecy may well be one of the reasons for adopting this view. However, I personally am persuaded that this view is incorrect. One conservative scholar makes the following points:

1. There is predictive prophecy in Isaiah 1-39 (often attributed to the “first” Isaiah who lived prior to the Babylonian Captivity). Thus, one does not escape predictive prophecy simply by asserting that chapters 40-66 were written later in history by another author. For instance, Isaiah 7:16, 8:4 and others are prophecies which were fulfilled shortly after they were given, whereas 9:1-2 is a prophecy about the coming of Messiah (fulfilled hundreds of years after it was given). Such examples could be multiplied.

2. Although there are some differences in the literary style of chapters 1-39 and 40-66, this does not at all mean that the entire book could not have been written by one person. After all, if such standards were applied to the works of Shakespeare or Milton, we would have to deny that they wrote much of what is attributed to them. Clearly, the same author can make use of diverse literary forms.

3. There are also similarities between both sections of Isaiah. For instance, compare 11:6-9 (allegedly by first Isaiah) with 65:25 (allegedly by second Isaiah). Other passages could be mentioned. Such passages argue as persuasively for a single author as any differences might argue for two authors.

4. Most importantly (in my view) is the New Testament use of Isaiah. First, quotations from chapters 40-66 (allegedly from “second” Isaiah) are simply attributed to Isaiah (see Matthew 3:3 and Acts 8:28-33 for just two examples). Second, in John 12:37-41, there are quotations from Isaiah 53:1 and 6:10, and both are attributed to the same Isaiah who saw the glory of the Lord (John 12:41).

Thus, I think there are good reasons for believing that there was only one author of the book of Isaiah.

Concerning the Gospels, I will certainly admit that there are some difficulties in harmonizing them on all points. However, I do think it’s possible to harmonize them in large part. Also, it’s important to remember that sometimes problems are resolved with the discovery of new data from archaeology, history and the like. This has happened many times in the past and will likely happen more in the future.

I take the traditional view on the origins of the Gospels. Namely, that Matthew and John were written by the apostles of those names, that Mark was written with eyewitness testimony supplied by the Apostle Peter, and that Luke was written by the physician, who thoroughly researched the subject before writing (see Luke 1:1-4). All of the Gospels were written in the first century, probably between the dates of the mid-50’s to early 60’s for Mark and the 90’s for John.

Hope this information helps put your mind at ease a bit.



Michael Gleghorn
Probe Ministries


Dr. Michael Gleghorn is both a research associate with Probe Ministries and an instructor in Christian Worldview at Grand Canyon University in Phoenix, Arizona.. He earned a B.A. in psychology from Baylor University, a Th.M. in systematic theology from Dallas Theological Seminary, and a Ph.D. in Theological Studies (also from Dallas Theological Seminary). Before coming on staff with Probe, Michael taught history and theology at Christway Academy in Duncanville, Texas. Michael and his wife Hannah have two children: Arianna and Josiah. His personal website is michaelgleghorn.com.

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