William Lane Craig writes in his Contending with Christianity’s Critics:

1. Openists have their own conception of what is dignum deo, and they don’t hesitate to draw on it when the Scriptures are silent. For example, if the openists are right that the Bible doesn’t clearly teach exhaustive omniscience with respect to the future, it’s no less true that it doesn’t clearly teach exhaustive omniscience with respect to the past and present; yet openists accept the latter. Why? Presumably because ignorance of any detail of the past and present would not be dignum deo.