What is "this generation" that Jesus spoke of in Matthew 24:34?
I, myself, believe that "this generation" in Matthew 24:34 refers to the present corrupted generation through Adam.
The Greek word often transliterated as "genea" -- in the Bible -- most often, but not always, refers to a specific generation of people living in a specific time.
Jesus linked the passing away of "this generation" with the passing away of the present heavens and earth. (Matthew 24:35) This would indicate the generation that Jesus was speaking of in Matthew 24:34 is the world of mankind as developed since Adam. It is the "world" spoken of in Romans 5:12, into which sin was introduced by means of one man. Now let us note what Paul wrote:
Philippians 2:14 Do all things without murmurings and divisive reasonings,
Philippians 2:15 that you may become blameless and harmless, children of God without blemish in the midst of a crooked and perverse generation [genea], among whom you are seen as lights in the world.
Paul used the same word in Philippians 2:15 that Jesus used in Matthew 24:34, and he associates it with "the world". The word "world" is translated from the Greek word often transliterated as "kosmos". It is the same word that Paul used in Romans 5:12, when he wrote of how sin had come into the world. It is also the same word that Jesus used in in John 17:5, and the same word John used in John 1:10. Therefore, my conclusion is that "this generation" of Matthew 24:34, being associated with the present heavens and earth that are to pass away (Matthew 24:35), is the world into which the Logos came, which became corrupted through the sin of Adam (Romans 5:12), resulting in the present rule of the sun of unrighteousness (crookedness) and vanity. -- Ecclesiastes 1:2,8-17; Romans 5:12-19; 8:20-22.
See my study: