© Michael Lacewing
Two puzzles about omniscience
This handout follows the handout on ‘The divine attributes’. Read that handout
first.
If God is the most perfect possible being, then each of the perfections attributed
to God must be possible, and the combination of the perfections must also be
possible. Both of these requirements lead to difficulties. In this handout, we
consider two puzzles about omniscience.
KRETZMANN, ‘OMNISCIENCE AND IMMUTABILITY’
Is omniscience possible? Is it possible for God to know everything, or at least
everything that it is possible to know? Norman Kretzmann argues that, as long as
we think that God cannot change – that God is ‘immutable’ – then God cannot be
omniscient. The thought that God cannot change comes from the thought that God
is perfect. Kretzmann argues:
1.
2.
3.
4.
5.
6.
7.
A perfect being is not subject to change.
A perfect being knows everything.
A being that knows everything always knows what time it is.
A being that always knows what time it is is subject to change.
Therefore, a perfect being is subject to change.
Therefore, a perfect being is not a perfect being.
Therefore, there is no perfect being.
This argument is a reductio ad absurdum, which is a form of argument that shows
that some claim leads to a contradiction. The contradiction is (6). If (1)-(5) are
true, then the concept of a perfect being is incoherent.
The most obvious premise to attack is (4). Kretzmann starts there.
1. Objection: Just because what time it is changes doesn’t mean that knowing
what time it is counts as a change in knowledge.
Reply: Yes it does. If you know first that it is 1.30 and then you know that it is
not 1.30 (because it is 1.40), you know one thing and then another. So what
you know changes.
2. Objection: A change in your beliefs like this doesn’t count as a change in you.
Reply: It’s true that you haven’t changed your mind or decided that you were
wrong. And it’s true that the change in your beliefs isn’t very significant. But it
is still true that your beliefs have changed, and so your mind has changed.
Two more objections attack premises (3) and (4) together:
3. Objection: God knows everything about the universe ‘simultaneously’, not
‘successively’. In other words, God knows everything ‘all at once’; his
knowledge doesn’t change as the universe changes. (For example, God might
know everything ‘all at once’ because God is transcendent.)
Reply: But this means that God cannot know what time it is now, and so is not
omniscient. Perhaps God knows the time at which each thing happens – past,
present or future. But that doesn’t mean that God knows when in time we are.
To know that involves knowing something that changes. If God doesn’t change,
then God doesn’t know where we are in time, so God is not omniscient.
4. Objection: God is transcendent, outside time. So God cannot change.
Reply: God’s transcendence is usually understood as there being no time from
God’s point of view. But that would mean that time is an illusion that we suffer
from. In turn, that means that it is never true to say ‘it is now 1.30 (or any
other time)’. If time doesn’t exist, then nothing changes. This is implausible, so
we should reject the idea of God’s transcendence.
Perhaps the difficulty is with our interpretation of omniscience (2).
5. Objection: Omniscience is not knowing everything, or everything that it is
possible to know. Omniscience is knowing what it is logically possible for a
perfect being to know. A perfect being transcends time. Therefore, it is
logically impossible for a perfect being to know what time it is. But not
knowing what it is logically impossible for a perfect being to know is no
limitation.
Reply: This form of argument is unsatisfactory. For instance, ‘I am a mortal
being, and so it is logically impossible that I should not die. Therefore, dying is
no limitation on me’. Obviously, dying is a limitation! The correct conclusion is
that a perfect being – one that both transcends time and is omniscient – is
logically impossible.
6. Objection: Omniscience is knowing everything that it is possible for a perfect
being to know without ceasing to be perfect. Knowing what time it is is only
possible if one changes, and to change is to be imperfect. Therefore, a perfect
being is omniscient without knowing what time it is. (One might argue that a
perfect being could know what time it is, but chooses not to because to know
that would mean becoming changeable.)
Reply: This is highly counter-intuitive. Knowing what time it is is knowing what
is happening now. To not know that is to lack significant knowledge. And it
won’t work to say that God chooses not to know everything: omniscience isn’t
merely the power to know everything; it is knowing everything.
Perhaps the problem, then, is thinking that in order to be perfect, God must be
unchangeable (1).
7. Objection: Knowing what time it is from one moment to the next is not a
change that affects God’s perfection. So God’s knowledge does change, in this
one small respect.
Reply: Being perfect has also meant being ‘complete’, never in a state of
potential. If God knows what time it is, God’s knowledge is – in this respect –
not complete; God is yet to know what time it is next.
Suppose nothing ever changed, including time. In such a world, God could know
everything and be unchangeable. So what makes omniscience and immutability
incompatible is a contingent fact, the fact that things change. So if God exists,
God isn’t the most perfect possible being – the most perfect possible being only
exists in a world in which nothing changes. At best, God is the most perfect actual
being – but that being can’t be absolutely perfect, because God must either
change or can’t be omniscient.
OMNISCIENCE AND HUMAN FREEDOM
If we were able to solve Kretzmann’s challenge to God’s omniscience, we would
still face another puzzle about the relation between God’s knowledge and time.
Can God know what I will do in the future? If God is eternal, existing outside time,
the problem doesn’t seem to arise. God already knows what happens in that period
of time which we call ‘future’. Being outside time, God’s knowledge of all events
is ‘simultaneous’. Past, present and future are all the same to God.
This response defends God’s omniscience (although it leads to some of the
problems above – see Objections (c) and (d)). But a new problem then arises. If
God knows what I will do in the future, are my actions free?
1. For me to do an action freely, I must be able to do it or refrain from doing it.
2. If God knows what I will do before I do it, then it must be true that I do that
action.
3. Therefore, it cannot be true that God knows what I will do before I do it and be
true that I don’t do that action.
4. If it is true that I do that action, then nothing I can do can prevent it coming
true that I am doing that action.
5. Therefore, if God knows what I will do before I do it, then I cannot refrain from
doing that action.
6. Therefore, if God knows what I will do before I do it, then that action is not
free.
7. (Therefore, conversely, if my actions are free, God does not know what I will
do before I do it.)
If I am free, then this argument entails that God does not know what I will do
before I do it. So there is something God does not know, and so God is not
omniscient. (For God not to have knowledge of the future, all time cannot be the
same for God, so God cannot be eternal, but in some way, must exist within time.)
Furthermore, as the future unfolds, God would gain new knowledge. Again, if God
gains knowledge, he wasn’t previously omniscient.
We could simply conclude that God is omniscient and we are not free. However,
this raises another conflict for the concept of God. Freedom – free will – is a great
good that allows us to do good or evil and to willingly enter into a relationship with
God or not. Without free will, we couldn’t choose how to live or what kind of
person to be, so our lives would not be meaningful or morally significant. As
supremely good, God would want our lives to be morally significant and
meaningful, so he would wish us to have free will. If we are not free, God is not
supremely good.
Can I be free and God be omniscient? We may argue that God’s not knowing what I
will do before I do it is not be a restriction on God’s knowledge. It is impossible to
know the future because of the existence of free will. So God still knows
everything it is possible to know at any given time. And God’s gaining knowledge
as time passes is consistent with God being omniscient: God always knows
everything it is possible to know. It is just that what it is possible to know changes
over time.
This reply accepts the argument (1)-(7) above, but claims that the argument does
not show that God isn’t omniscient. But is this a satisfactory view of omniscience?
Kenny, ‘Divine foreknowledge and human freedom’
Anthony Kenny defends a different solution which rejects the argument (1)-(7). He
argues that it is possible both for God to know what I will do before I do it and for
me to do that action freely. He begins (p. 258) by objecting to premise (2).
Generalized, the claim is ‘If God knows that p, p must be true’. This can be
understood in two ways, one true and one false:
False: ‘If God knows that p, it is necessarily true that p’.
True: ‘The proposition ‘whatever God knows is true’ is necessarily true.’
The false reading misleads us into thinking about whether our actions are free. We
said that if God knows what I will do tomorrow, then it must be true that I do that
and nothing else. So I must do it, I cannot not do it, and so I am not free. But the
claim is false – there is no reason to think that whatever God knows is a necessary
truth. God can know all sorts of contingent truths.
The true reading simply follows from the definition of knowledge. No one can know
what is false. But this reading doesn’t obviously cause a problem for freedom.
Knowing that something will happen doesn’t mean that it has to happen. So for
God to know what I will do tomorrow, it only needs to be the case that I don’t do
something else. It doesn’t mean that I can’t.
But we may object that this doesn’t solve the problem (p. 264).
1. To do something different from what God knows I will do would mean changing
God’s knowledge – either changing what God knows (I will do) or making it that
God doesn’t know what I will do, because I do something else.
2. If God already knows what I will do, then changing what God knows would
mean changing the past.
3. I can’t change the past, so I can’t change what God knows.
4. So I can’t change what I will do.
5. So there is nothing I can do except what God already knows that I will do.
Kenny’s response is technical and difficult: We don’t change the future (p. 266) –
the future is what happens when all the ‘changes’ (decisions, choices, etc.) are
done. The future is what will happen. The past is what has happened. There are
truths about both. By acting, I don’t change the future. Instead, I can change a
truth about the future into a truth about the past: ‘I will write this book’ (future
tense) turns into ‘I have written this book’ (past tense). But, says Kenny, I can
equally change a truth about the past: ‘I have not written this book’ (past tense)
becomes ‘I have written this book’ (past tense).
We are supposing that God’s belief about what I will do is true; when I do what
God believes I will do, that makes his belief true. That doesn’t show that I can’t
choose or decide what to do; it doesn’t show that I cannot act freely.
Discussion
Kenny’s solution is perplexing. Technically, he may be right that the argument
given does not show that God’s knowledge of what I will do rules out freedom.
However, as soon as we ask how it is that God knows what I will do, the puzzle
arises again.
Clearly, simply having a true belief that someone will do something doesn’t mean
that they are not free. For instance, perhaps you can accurately predict that a
friend of yours will help this old lady across the street, because he is a kind
person, in a good mood, and has just said that this is what he will do. In this
instance, your belief is not only true, but justified as well, so we are happy to say
that you know what your friend will do. Or again, if your beliefs about what your
friend does are generally reliable, then you know what he will do.
But we cannot suppose that God’s knowledge of what I will do is like this. Because
God is omniscient, his beliefs are not merely reliable, but complete and infallible.
How can there be complete and infallible knowledge of what someone will choose
to do if that choice is not already determined in some way? The justifications we
offered above, e.g. knowing someone’s character, might give you knowledge of
the general shape of their choices and actions, but not every minute detail. And it
certainly won’t be enough for knowledge of what they will be doing in the distant
future. If God knows now what I will be doing on May 23rd, 2026, this can’t simply
be because he knows my character well! For a start, God must know whether I will
be alive then, and could only know that if the future is fixed in some way. But if
the future is fixed, can we act freely?