Jesus said, "I tell you the truth, this generation will certainly not pass away until all these things have happened" (Matthew 24:34).C.S. Lewis believed that the words of Jesus in Matthew 24:34 conveyed His belief that all events associated with His Second Coming would transpire within the lifetime of his hearers. Lewis pointed out that these words of Jesus are recorded by two other gospel writers in Mark 13:30; Luke 21:32, so Jesus' belief in His soon-to-be Second Coming was something all the disciples heard Him declare.
A generation in the Hebrew mindset of Jesus' day was a lifetime or forty years. However, because Jesus did not return within the lifetime of those who heard Him say this, Lewis declared Matthew 24:34 "is certainly the most embarrassing verse in the Bible."
C.S. Lewis was a contemporary of Albert Schweitzer. Christian theology in Europe during the 20th century (Lewis' lifetime) came under the direct influence of Albert Schweitzer's book The Quest for the Historical Jesus. Schweitzer. an accomplished musician, theologian, philosopher, physician, and humanitarian in his own right, proposed that Jesus and His disciples were obsessed with a very imminent end of the world. Since the world did not end the first century, Schweitzer convincingly argued that Jesus was mistaken about His own return. This mistake by the historical Jesus, according to Schweitzer, is cause for embarrassment among all evangelical Christians, particularly those of us who live 2,000 years after Jesus declared He was coming soon.
C.S. Lewis' solution to this embarrassment is to propose that Jesus in His human nature was actually ignorant of the time of His own return.
"To believe in the Incarnation, to believe that Jesus is God, makes it hard to understand how He could be ignorant. Yet it would be difficult, and to me, repellent, to suppose that Jesus never asked a genuine question, that is, a question to which he did not know the answer. That would make his humanity something so unlike ours as scarcely to desrve the name. I find it easier to believe that when he said, "Who touched me?" (Luke 7:45) he really didn't know." (C.S. Lewis, The World's Last Night).The only problem with Lewis' explanation, at least in my mind, is that Jesus wasn't asking a question of the Father about His return, He was declaring a truth to the disciples about His return. "I tell you the truth, this generation will certainly not pass away until all these things have happened" (Matthew 24:34).
Jesus' words convey certainty, not doubt.
Lewis would later use the famous trilemma to confront peoples' opinion of Christ. "Jesus is either a liar, a lunatic, or He is Lord."
I believe Jesus is Lord, and for that reason, when Jesus speaks with certainty, it certainly happens just like He says it will.
The reason many Christians, even wonderfully astute thinkers like C.S. Lewis, have such an embarrassing time with Matthew 24:34 is because they wrongly think Jesus is referring to the end of the world. He wasn't. Jesus was referring to His coming to end the Old Covenant age by destroying the Temple and the system of worship built around the Temple.
That happened in A.D. 70 - within a generation of His words in Matthew 24:34.
Once Christians begin to understand that the Kingdom of God which Christ came to establish looks so much different from the Hebrew Kingdom of Old Covenant Israel, any confusion dissipates. Jesus promised His hearers, "within this generation," to end the entire system of Old Covenant worship. He did exactly what He said He would do. He came to establish a New Covenant with the world and to inaugurate His eternal Kingdom through His fulfillment of the Law and the Prophets. When we understand how Christ came to "make obsolete" the Old Covenant (see Hebrews 8:13), then we'll begin to focus more on what the Kingdom of God today looks like today rather than looking for something to come. The Kingdom of Christ is already here.
The Temple of God - is every believer in Christ' it's a people, not a building.
The Priests of God - are those who believe in Christ; it is no longer a hierarchal system of spiritual authority.
Worship - is in Spirit and in truth every day; not in a building once a week.
Law - is simply to "Love one another as Christ loves us": not the Law of Old Covenant Israel.
Life - is led by the Spirit, not regulated by laws of a church, a man, or a system of worship, but only by the Royal Law of love.
All the promises of God are "yes and amen" in Jesus Christ (II Corinthians 1:20), who "fulfilled the Law and the Prophets," made obsolete the Old Covenant system of worship through His death, burial and resurrection (Hebrews 8:13), and gave His followers certain promise that He would soon return and destroy the age of Law which they grew up in (Matthew 24:34). So when it comes to living out the life Jesus calls you to live, you are to "Listen to Him!" (Luke 9:35).
The reason many evangelicals struggle with Matthew 24:34, especially evangelicals from a Presbyterian, Episcopal, or Reformed Protestant background like C.S. Lewis as well as Pentecostals, Charismatics and Dispensationalists who are unlike C.S. Lewis, is because all these Christian groups have a tendency to try to merge the old age (e.g. "the Old Covenant") with the new age (e.g. "The New Covenant"). When you merge the Covenants, you have a difficult time seeing how all the eschatological talks of Jesus (e.g. His "end times" talks) and the apostles are about the END of the OLD COVENANT and not the end of the physical world or the universe.
After Christ died and rose from the grave, He fulfilled the promise He gave to His early disciples and returned in judgment to abolish the very thing which prefigured Him (The Temple and the Law).
There's no need for embarrassment when it comes to Matthew 24:34.
Christians need to know Jesus simply told His disciples He was coming back within a generation to end the old age that He came to make obsolete, not the world.
And He did.