On the Open Theism Facebook page, John asks:
How do we explain Genesis 15:13 “God said to Abram, ‘know for certain that your descendants will be enslaved in a Foreign land for 400 years?”
In response, an article was posted by Gregory Boyd:
This passage may constitute a conditional prophecy which could have been modified had circumstances called for it. Many if not most prophecies in the Bible are conditional (cf. Jer. 18:7–10). They are not mere previews of an unalterable future. They rather reveal God’s present intentions, assuming things don’t change.
On the other hand, the passage may indeed constitute an unconditional prophecy. In this case the passage reveals a now-unalterable feature of God’s providential plan. The sovereign Lord of history who is ultimately in control of the movement of the nations (Acts 17:24–28) deemed it wise to ensure that his future people would be in captivity for four centuries. It is important to note, however, that the Lord would not need to control and/or foreknow every other detail about human history to accomplish this. The Lord of history who grants whatever degree of freedom he wishes to grant to his human subjects can control and foreknow aspects of the future and guide history toward his desired goal without micro-controlling and foreknowing every detail along the way.