Preterism is the Christian eschatological (understanding of end time events) concept that all Bible prophecy has already been fulfilled including Yeshua’s Matthew 24 Olivet Discourse and those prophecies in the book of Revelation.
I will say that it is my belief that preterism is an over simplistic concept that often fails to take into account several things:
a) The dual or even multiple fulfillments of certain biblical prophecies. Even the Jewish sages who’ve been studying the OT scriptures for millennia recognize the often cyclical nature of some prophecies in that many have multiple fulfillments. It seems that the preterist looks at prophecy in more a linear (timeline) Greco-Roman perspective rather from the Hebraic, more cyclical nature in which the Bible was written. This is to their detriment and causes them to have a skewed view of biblical prophecy.
b) That some prophecies have been indeed fulfilled, while others are yet to be fulfilled, and yet still others have been fulfilled and will be fulfilled in a greater sense in the future.
c) They often fail to fully understand historical events. The preterist view of Olivet Discourse Matt 24 is a prime example. While it appears that some of the things Yeshua predicted in Matthew 24 have a AD 70 fulfillment, other events listed in this chapter clearly don’t unless you “cram it to fit and paint it to match” as preterists like to do. This they do by applying some things in a given prophecy in a literal sense, and then when a prophecy can’t be interpreted literally to fit historical events, they simply allegorize it away by making the prophecy symbolic. In my opinion, this is a dangerous approach and is playing fast and loose with the Bible. You can make the Bible say virtually anything you want it to say when you do this. This is a hermeneutical problem where they make the Bible say what they want it to say (eisegesis) instead of letting the Bible speak for itself (exegesis).
d) The preterist usually fails to understand Israel in history, who the people of Israel are,