Immutable Knowledge
If prior cognizance would cause Him to change His decree, His decree could not have been true, earnest, and sincere. Or it suggests that His change of intent is due to His inability to execute His will either because man prevents Him from doing so, or because God's nature is mutable, thus causing Him to change His mind. Neither of the aforesaid can be true concerning God.
Wilhelmus à Brakel, The Christian's Reasonable Service, ed. Joel R. Beeke, trans. Bartel Elshout, vol. 1 (Grand Rapids, MI: Reformation Heritage Books, 1992), 116.