Christians often make the claim that God knows everything. If asked for specifics, theyll say this includes knowledge about the future (foreknowledge) and that such knowledge is infallible. Christians also often make the claim that man has free will. Upon being asked for specifics, theyll agree that free will entails the ability to freely make a choice and that up until the time an option is chosen, a different option could have been chosen. At quick glance, these claims may not appear to be in conflict. However, if we dig a little deeper into each of these claims, well see that they are.
Lets say Fred is faced with a free choice of A or B. He is due to make this choice on Tuesday (day 2). Well call Freds day 2 A/B choice variable Y. This means prior to day 2, variable Y has no value (or the choice lies in an unmade state), and on day 2, variable Y will acquire a value of either A or B to be decided freely by Fred.
Given the Christian claim that God has infallible foreknowledge, this would mean God knows infallibly what A/B choice Fred will make when the choice still lies in an unmade state. To gain further clarity on this, it can be asked, if it were asked on day 1 does God know infallibly what Freds day 2 A/B choice will be, would the answer be YES?. Christians would typically agree.
If asked for further specifics, such as what if Fred chooses something in conflict with what God knows he will choose, Christians will respond with the assertion that Fred will choose whatever God knows he will choose.
So well call Gods day 1 knowledge of Freds day 2 A/B choice variable X. If God knows infallibly on day 1 what Freds day 2 A/B choice will be, then it follows that X has a static or fixed value of either A or B as of day 1.
We now have three conditions:
1) X (or God's knowledge as of day 1 of Fred's day 2 A/B choice) has a value of either A or B on day 1 and this value is fixed and cannot change. If it is A, it will remain A. If it is B, it willremain B. This follows the assertion that God has infallible knowledge of future events.
2) Y (or Freds day 2 A/B choice) receives its value on day 2. Once Y receives its value, it becomes locked. Prior to receiving its value, it could potentially become A or B, as Fred freely chooses A or B. This follows the assertion that Fred has free will or can freely make choices.
3) X is equal to Y. This follows the assertion that whatever Fred chooses is precisely the same as what God knew he would choose.
Not all three of these conditions can be true.
If #1 & #2 are true, then #3 cant be true, as X wouldnt be equal to Y, nor would Y be equal to X. Not only would X receive a value at a different point in time than Y, but Y could be assigned a value in conflict with the static value of X.
If #1 & #3 are true, then #2 cant be true. Fred wouldnt be able to freely choose A or B, as variable Y would already be defined as being equal to variable X. Christians will often argue that God's knowledge of Freds future choice is a function of Freds day 2 choice. But this doesnt hold true if the answer to the question if asked on day 1, does God know what Freds day 2 A/B choice will be? is YES.
If #2 & #3 are true, then #1 cant be true. What this means is if variable Y gets its value on day 2, then variable X also gets its value on day 2 and gets the same value as variable Y. It then follows that God cant have infallible knowledge on day 1 of Freds day 2 A/B choice.
Therefore, it is logically impossible for God (or anyone) to have infallible foreknowledge of a yet to be made free choice.