It is not the development(dispensation) of God's word to man that is the question, but the erroneous doctrine(s) that were made by men and heralded under 'Dispensation'.
The #1 heresy of 'Dispensation' is the separation of Jew from Gentile in Christ.
Although if you go by DavidTree's reasoning, you could literally have hundreds of such divisions, so the number is totally arbitrary, not Biblical by any stretch. There are other problems with their beliefs about these divisions, however.
1. They believe that each period is totally unlike any other period, which is false right from the start. For example, they would say that there's no Law in the period of Grace and there's no Grace in the period of Law. Both are incorrect. They would say there's no Human government in the period of Promise, also not true. Abraham and his sons came into contact with lots of governments. Or there's no Conscience in the other periods, when in fact, God has always dealt with man, appealing to his conscience.
So there's really only 2 great divisons in the Bible - the Old Covenant and the New Covenant.
2. They like to show a diagram of seven horizontal squares, saying that each square represents one of the "seven dispensations" implying that each "dispensation" is 1000 years long. That's very convenient (but it's not true), since the 7th square is the Millennium, which is 1000 years.
The problem is that some of their periods are much less than 1000 years, by several hundreds of years, others are longer than 1000 years.
It is impossible that the "dispensation of Innocence", which is Adam and Eve's time in the Garden of Eden before the fall, was 1000 years long. How do we know this? Because Genesis 5:3 tells us that Adam lived 130 years when he became the father of Seth. Adam was created on the 6th Day, so what recorded events happened between his creation and the time he had his son, Seth? Well God rested on the 7th Day, the fall of Man, their punishment, He kicked them out of Eden, the story of Cain and Abel. Then we read that Adam, at 130, has Seth. So notice that the 7th Day is within the 130 years of Adam's life, so the 7th Day Must be less than 130 years. In fact, I believe the 7th Day was Much less - just 24 hours like the days are today. So the "dispensation of innocence" ended with the Fall of Man, which also occurred during that 130 period of Adam's life, so there's no way it could be anywhere close to 1000 years.
Also the period of the Law was much longer than 1000 years - it lasted around 1300 to 1500 years.
3. Also they say that each "dispensation" has its own method of getting saved. One example is, they say, during the Millennium, people will get saved by obeying the Mosaic Law. How unbelieveable! Man has always been saved by grace through faith - from Abel to us today - that won't change.
These are just the tip of the iceberg, when it comes to problems with "dispensationalism".
