Philosophers and theologians have often defined “divine omniscience” as “God’s knowledge of the truth value of all meaningful propositions.” I completely agree with this. Unfortunately, they typically assumed that propositions about what “will” and “will not” occur exhaust the field of meaningful propositions about the future. They thus concluded that God eternal knows all that will and will not take place and that there is nothing else for God to know.
This is a mistake, however, because propositions about what “might and might not” take place are also meaningful, and God must therefore know the truth value of these. Moreover, the opposite of “might” is “will not,” and the opposite of “might not” is “will.” So, if a “might and might not” proposition is true, then the corresponding propositions about what “will” and “will not” take place are both false.
For example, if its true that “Greg might and might not buy a blue Honda in 2016,” then its false that “Greg will (certainly) buy a blue Honda in 2016” and false that “Greg will (certainly) not buy a blue Honda in 2016.” So too, if it ever becomes true that “Greg will (certainly) buy a blue Honda in 2016” or true that “Greg will (certainly) not buy a blue Honda in 2016,” then it will be false that “Greg might and might not buy a blue Honda in 2016.” And since God knows the truth value of all propositions, God would know precisely when it is true that I “might and might not” buy this car and when it becomes true that I either “will” or “will not.” God thus faces a partly open future.
This is controversial. Why assume that statements about what “might” happen contradict those about “will not”? It seems this sort of statement is meaningful too: “I could run through the streets naked in the next 5 minutes, but I will not. The “could” here expresses the possibility of those (terrible) states of affairs, and the “will not” expresses that they shall not come to pass, owing to my rational choice. There is nothing contradictory about saying this sort of thing, but the semantic analysis Boyd gives of “might” would make it so. Thus, we have reason to doubt his analysis.