Open theism leaves the traditional or classical teaching of many of God's attributes.  It also may be called Free-Will Theism, Openness of God, or Neo-Theism.  It has recently been developed and popularized by Clark Pinnock, Greg Boyd, Richard Rice, John Sanders, William Hasker, and David Basinger, who have come out with a number of books on the subject.  It has spurred much controversy within evangelical circles. 

Below are only a few points where open theists differ from classical theism:

1. God does not have absolute foreknowledge.  He chooses to know some things in the future and not others.  The future is "partly open," hence, Open Theism.  This abandons the classical view of God's omniscience.
2. God's love is His foremost attribute.  While traditional theist would not argue that God is love, in this system it is elevated at the expense of other attributes, most namely God's wrath and justice.
3. God is constrained by time.  He "experiences the temporal world in a temporal way"¹.  This abandons the classical teaching of omnitemporality.
4. God is profoundly influenced by man and by the world.  They stop short of being process theologians, and indeed would argue against that theology, but abandon the classical view of divine immutability.
5. Open theists believe that there is prophecy in the bible which goes unfulfilled, that God's plans can be thwarted.  Indeed, "God's will does not guarantee the outcome that He desires."².  This goes against the classical teachings of God's omnipotence and sovereignty.