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#187 Does Knowledge Require Certainty?

November 14, 2010
Q

Dear Doctor Craig,

I have been studying the defense of the Christian faith for the better part of six months now. I acknowledge the fact that six months is not a vast amount of time; however there has been one idea that I have not been able to surmount or give a dispute when brought up in conversation or debate. Many people, some Christians included, plead intellectual ignorance as it applies to knowing anything about life, the universe, or logic. They state that since every possible option has not been explored that nothing can be said for certain. Since nothing can be said for certain, all of the premises that you pose may seem true to us, but we cannot say they are absolutely true. If they cannot be proven absolutely true, then there is no reason to believe them, and the argument dies right there.

It is becoming increasingly frustrating and disheartening to begin to speak to someone based on logic that is accepted and proven, and then be stopped before a discussion can even begin. For instance in the Kalam Cosmological Argument, the first premise states "Everything, that begins to exist, has a cause." But many people question that premise due to the fact that we humans have not traveled the extent of the universe to conclude that premise. Because we have not explored the possibilities of the rest of the universe, it is impossible to base something off of an idea that may or may not be true in the whole universe.

I am sure that you have heard this before in debates, this idea of uncertainty of anything. I am very unsure of how to proceed in talking to people when they think this way. What advice would you give for responding to these objections?

Christopher

United States

Dr. craig’s response


A

The folks you mention, Christopher, are victims of an unjustified and ultimately self-defeating scepticism.

Notice that they equate knowledge with certainty. If you’re not certain that some proposition p is true, then you do not know that p. But what justification is there for that assumption? I know that I have a head, for example. But I could be a brain in a vat of chemicals being stimulated by a mad scientist to think that I have a body. Does this mere possibility imply that I do not know that I have a head? If your friends answer, “Yes,” ask them for their justification for thinking that knowledge requires certainty. Anything they say, you can reply to by asking, “Are you certain of that?” If they say, “No,” then they don’t know that knowledge requires certainty. If they say, “Yes,” then it’s not true after all that we can’t know anything about life, the universe, or logic.

Scepticism, ironically, draws its life’s blood from claims to have a good deal of knowledge. For example, your friends claim to know, “Since every possible option has not been explored, nothing can be said for certain.” That statement is itself a claim to knowledge! (A claim that is patently false, but never mind!) How do they know that? Or again, how do they know that “Since nothing can be said for certain, we cannot say that your premisses are absolutely true”? This is a claim to knowledge (again, funnily enough, a false claim, but never mind). Or how about the claim, “If the premisses cannot be proven absolutely true, then there is no reason to believe them”? How do they know that? (Again, this seems patently false, but leave that to the side.) Where do these sceptics come up with all this knowledge?

And if we cannot know anything about logic, how can they reason:

1. Since every possible option has not been explored, nothing can be said for certain.

2. Since nothing can be said for certain, all of the premises that you pose may seem true to us, but we cannot say they are absolutely true.

3. If they cannot be proven absolutely true, then there is no reason to believe them.

That looks to me for all the world like the premisses for the logical inference form called Hypothetical Syllogism! But if that inference rule is not true, then no conclusion follows from (1-3) and we have no reason to doubt my original argument.

The fundamental problem with scepticism is that it presupposes that in order to know p, you must know that you know p. But if I can know some truth without knowing how it is that I know it, then the nerve of scepticism is severed. The sceptic actually is making a very radical claim, for which he cannot provide any justification without pulling the rug from beneath his own feet.

Scepticism is thus strangely presumptuous and self-defeating. It relies on our having knowledge of some very non-obvious claims. The sceptic cannot provide any justification of those claims, lest his view becomes self-referentially incoherent; yet without them his scepticism collapses, for then my lack of certainty does not imply that I have a lack of knowledge.

- William Lane Craig