Philosophy of Religion (booklet)

Problems with Divine Omniscience

Christian theists claim that God is omniscient, i.e. all-knowing. The doctrine of divine omniscience, though, faces several philosophical objections; there are a number of arguments in the philosophy of religion that purport to demonstrate that God cannot possibly know everything. These include arguments that the doctrine of divine omniscience is logically incoherent, that it is inconsistent with the further Christian doctrine of divine impeccability (i.e. the doctrine that God cannot sin), and that it is refuted by the fact of human freedom.

If any of these arguments is successful, then the doctrine of divine omniscience as it is usually taught will require at least modification, and possibly abandonment. Further, if being omniscient were thought to be a part of what is involved in being God, then these arguments against the doctrine of divine omniscience might even constitute proofs of atheism, of the non-existence of God. Four problems with divine omniscience are worthy of mention.

The first problem - the paradox of omniscience - is derived from Cantor’s proof that there is no set of all sets. Omniscience, it is said, entails knowledge of the set of all truths. Cantor’s proof, however, demonstrates that there is no such set. As there is no such set, it is argued, there can be no omniscient being.

The second problem is the problem of experiential knowledge. Here the argument is that there are certain facts knowledge of which can only be acquired through certain experiences - knowledge of what it is like to sin, for instance, can only be acquired by sinning - and that some of these experiences, and so some of these items of knowledge, are such that they cannot be had by God.

The third problem is that of reconciling freedom and foreknowledge, specifically the existence of divine foreknowledge with the existence of human freedom. If God knows all of our future actions, then the future is fixed, but if the future is fixed, it seems that there is nothing that we can do to change it. The ability to determine our future actions, though, is what constitutes human freedom. Divine foreknowledge, then, seems to preclude the possibility of our being free agents.

The fourth problem is the problem of middle knowledge. Middle knowledge is knowledge of what free agents would have done had the world been other than it is. As the agents are free, their choice of action cannot be determined by the state of the world, and so cannot be calculated on that basis. As middle knowledge concerns counterfactual situations, however, neither can their choice of actions be known by observation of the future. With the two possible sources of knowledge ruled out, it seems that middle knowledge is an impossibility.

Problems with Experiential Knowledge

The second type of argument commonly advanced against the doctrine of divine omniscience is the problem of experiential knowledge. The problem of experiential knowledge is that there appear to be certain kinds of knowledge that can only be acquired by having certain kinds of experiences. One can only learn what it is like to sin by experiencing sin first-hand; one can only learn what it is like to feel malice by experiencing malice first-hand; one can only learn what it is like to be ignorant and powerless by experiencing ignorance and impotence first-hand. Some of these experiences, though, such as those listed above, are of a kind that cannot be had by God. God cannot sin, or feel malice, or lack power. If, though, there are facts that can only be known through experience, and God cannot have the experiences by which those facts can be known, then God cannot know those facts. In that case, though, the doctrine of divine omniscience will have been disproven.

(1) There are some items of knowledge that can only be acquired through experience.

(2) Some of the experiences through which items of knowledge that can only be acquired through experience are acquired are such that they cannot be had by God.

(3) If some of the experiences through which items of knowledge that can only be acquired through experience are acquired are such that they cannot be had by God, then there are some items of knowledge that cannot be acquired by God.

Therefore:

(4) There are some items of knowledge that cannot be acquired by God.

(5) If there are some items of knowledge that cannot be acquired by God then it is not the case that God is omniscient.

Therefore:

(6) It is not the case that God is omniscient.

How Does God Know the Future?

Christian theism claims that God is omniscient. With the exception of a recent movement know as “Open Theism”, omniscience has always been taken to entail knowledge of the future. If God is omniscience, then he knows not only everything about the way that the world is, but also everything about how the world will be.

How, though, can anyone know the future? And how, in particular, is it possible to know the future in such detail? There are two models of divine foreknowledge - the predictive model and the observational model - that seek to give answers to these questions.

The predictive model of divine foreknowledge holds that God knows the future by prediction, by calculating the way that the world is going to be on the basis of the way that the world is now. There are laws of nature that govern the way that the different entities in the world interact. Using these laws, even we, with our imperfect knowledge, can often make accurate predictions about the future. Think about the way that we calculate the future positions of satellites orbiting the Earth. We know where the satellites are now, and what laws govern their interactions, and so project where they will be in the future.

According to the predictive model of divine foreknowledge, God’s foreknowledge is derived from calculations such as these but on a much grander scale. Given perfect knowledge of the present state of the world, and perfect knowledge of the laws that govern the interaction of its parts, it seems, it should be possible to predict with perfect accuracy the way that the world will be at any given point in the future. This, according to the predictive model of divine foreknowledge, is how God knows, in perfect detail, what will happen in the future.

The problem with the predictive model of divine foreknowledge is that it only works given the assumption that determinism is true. Determinism holds that each state of the world wholly determines the subsequent states of the world; given the way that the world is now, determinism holds, there is only one possible way in which the rest of history could play itself out. This assumption is necessary for the predictive model of divine foreknowledge to work, because if there were several ways in which the rest of history could play itself out then, even with perfect knowledge of the present, and perfect knowledge of the laws of nature, God could not know for certain which of those possible futures would come about. If the present does not determine the future, then the future cannot be predicted with certainty.

Determinism, though, does not seem to be true. Quite apart from the scientific concerns about indeterminacy involving small particles, indeterminacy seems to enter the world through the choices of free agents. If any of us has genuine, significant freedom, it seems, then it cannot be the case that our future actions are determined by the present state of the world. To be a free agent is to be able to react to the world in any one of several ways, to choose which of several possibilities to realise. If there are free agents, then there are many possible futures. Perfect predictive foreknowledge, then, will be impossible.

Some have sought to resolve this problem with predictive foreknowledge by defending a position know as “compatibilism”. Compatibilists hold that we can have significant freedom even in a deterministic world; as long as it is facts about us that determine how we are going to act, they say, our decisions about how to act are free. If this position is defensible, then it allows the theist to hold both that God has perfect foreknowledge on the basis of prediction and that we are free.

An alternative defence of divine foreknowledge, however, is to reject the predictive model of divine foreknowledge and instead advance an observational model. The observational model of divine foreknowledge holds that God knows the future not by carrying out complex calculations about how the present might play out, but simply by observing it. God exists outside time, the observational model holds, and so is able to directly observe different points in time just as we can directly observe different points in space. On the observational model of divine foreknowledge, it doesn’t matter whether or not determinism is true, because God’s knowledge of the future is based not on predicting how the world will be in the future but on seeing how the world is in the future.

Freedom and Foreknowledge

The argument from foreknowledge is an argument that divine omniscience, or more specifically divine foreknowledge, is inconsistent with human freedom. The argument begins with a consideration of the consequences of God knowing everything. If God knows everything then he knows every act that each of us is going to perform in the future. If God knows every act that each of us is going to perform in the future, though, then it is not possible for any of us not to perform those acts. For if it were possible for any of us not to perform those acts then it would be possible for us to bring it about that that which God knows is false. Knowledge, of course, by definition, is knowledge of the truth; one cannot know that which is false. The idea that that which God knows could be false is therefore absurd. Because God’s omniscience entails knowledge of all of our future acts, therefore, it also entails that it is impossible for any of us not to perform those acts.

The argument continues with a consideration of freedom. Freedom, it seems, consists precisely in the ability not to do that which we do, in there being a plurality of acts each of which it is possible for us to choose to perform. If one does not have this ability to choose, i.e. if there is no plurality of acts that it is possible for one to choose to perform, then one cannot be free. If God’s omniscience entails that it is impossible for any of us not to perform those acts that we are going to perform, therefore, then it also entails that none of those acts will be free.

For those that believe that human beings can and do perform acts freely and will continue to do so, the argument from foreknowledge can easily be pressed into service as an argument against the existence of God. For if the existence of an omniscient god is inconsistent with any of our future acts being free, as the argument from foreknowledge appears to demonstrate, then the existence of one free future act entails the non-existence of an omniscient god. Omniscience, though, is a part of the Christian conception of God. If no omniscient god exists, then God does not exist.

The argument from foreknowledge, presented as an argument against the existence of God, may therefore be formalised as follows:

(1) A necessary condition for an act's being free is that it is possible for the agent that is going to perform the act not to perform it.

(2) If God knows that an agent is going to perform an act, then it is not possible that the agent is not going to perform it.

Therefore:

(3) If God knows that an agent is going to perform an act, then it is not the case that that act is free.

(4) If an omniscient God exists, then if an agent is going to perform an act then God knows that that agent is going to perform that act.

Therefore:

(5) If an omniscient God exists, then if an agent is going to perform an act then it is not the case that that agent is going to perform that act freely.

(6) There is an agent that is going to perform an act freely.

Therefore:

(7) It is not the case that an omniscient God exists.

One possible concern with the argument from foreknowledge is that it appears to equivocate between different senses of "possible". The "possible" in (1), arguably, does not have the same meaning as the "possible" in (2). The “possible” in (1) appears to mean “possible given everything that is logically prior to the agent’s decision to perform the act”. The “possible” in (2) appears to mean “possible given everything that is logically prior to God’s knowledge that the agent will perform the act”. If there is some significant difference between the senses of “possible” used in (1) and (2), of course, then the argument will fail. A demonstration that God’s knowledge that the agent will perform the act entails that it is impossible in one sense--the sense in (1)--that the agents will not perform the act is not a demonstration that it is impossible in some other sense--the sense in (2)--that the agent will not perform the act. If the argument from foreknowledge equivocates on senses of “possible” in this way, then, then (3) will not follow from (1) and (2).

An alternative response to the argument from foreknowledge invokes the argument from future facts. The argument from foreknowledge purports to demonstrate that divine omniscience is inconsistent with future human freedom. What appears to be inconsistent with future human freedom, though, is not the existence of a being that knows facts about the future, but the existence of those facts about the future whether they are known by any being or not. The argument from foreknowledge can, it seems, be stripped of all references to God knowing the future without losing any of its force. What remains after this process is an argument that there are no truths about the future, a counter-intuitive conclusion. If this argument is unsound, if there are facts about the future, then the argument from foreknowledge must also be unsound. If this argument is sound, if there are no facts about the future, though, then God’s knowing all facts would not threaten human freedom; premise (4) of the argument from foreknowledge would be false. Either way, then, the argument from foreknowledge fails.

The Argument from Future Facts

The argument from foreknowledge purports to demonstrate that divine omniscience, or more specifically divine foreknowledge, is inconsistent with human freedom. It is arguable, however, that it is the existence of facts about the future, rather than the existence of a being that knows those facts about the future, that is difficult to reconcile with human freedom.

The argument from foreknowledge can, it seems, be stripped of its theological content without losing any of its force. To do this, references to God knowing that an agent is going to perform an act must be replaced with references to it being a fact that that agent is going to perform that act, and references to the existence of an omniscient God must be replaced with references to the existence of facts about the future. The result of this revision of the argument from foreknowledge will be referred to as the argument from future facts. This argument runs as follows:

(1) A necessary condition for an act's being free is that it is possible for the agent that is going to perform the act not to perform it.

(2) If it is a fact that an agent is going to perform an act, then it is not possible that the agent is not going to perform it.

Therefore:

(3) If it is a fact that an agent is going to perform an act, then it is not the case that that act is free.

(4) If there are facts about the future, then if an agent is going to perform an act then it is a fact that that agent is going to perform that act.

Therefore:

(5) If there are facts about the future, then if an agent is going to perform an act then it is not the case that that agent is going to perform that act freely.

(6) There is an agent that is going to perform an act freely.

Therefore:

(7) It is not the case that there are facts about the future.

This argument, it seems, is no worse than the argument from foreknowledge. Its premises are no less plausible than those of the argument from foreknowledge, and it has exactly the same logical structure. It may be, of course, that both arguments are unsound, but it is not the case both that the argument from foreknowledge is successful and that the argument from future facts is not. The advocate of the argument from foreknowledge therefore faces a dilemma.

The advocate of the argument from foreknowledge could, on the one hand, reject the argument from future facts as unsound. If he does this, though, then he must concede that the argument from foreknowledge is also unsound. For if he rejects the argument from future facts on the ground that one of its premises is false, then he must concede that the corresponding premise of the argument from foreknowledge is false, and if he rejects the argument from future facts on the ground that it employs faulty logic, then he must concede that the argument from foreknowledge similarly employs faulty logic. Rejection of the argument from future facts, then, is inconsistent with advocacy of the argument from foreknowledge.

The advocate of the argument from foreknowledge, therefore, must accept the argument from future facts as sound, conceding that there are no facts about the future. Once this concession is made, however, the threat to theism presented by the argument from foreknowledge vanishes. For the argument from foreknowledge is the argument that divine omniscience entails divine foreknowledge, but that foreknowledge is impossible given the fact of human freedom, and so that the fact of human freedom entails that no omniscient being exists. If there are no facts about the future, however, then omniscience - i.e. knowledge of all facts - does not entail knowledge of facts about the future, and so the impossibility of divine foreknowledge does not entail the impossibility of divine omniscience.

Whatever view is taken of the argument from future facts, then, the argument from foreknowledge must be abandoned.