Have you ever found yourself at a loss as to what your reply should be to a “doubter” of your faith?
Here is how to answer most of what you’ll run across.

A List of Self-refuting Statements

• You can’t know anything for sure.
Are you sure of that?

• You can’t know anything.
Do you know that?

• No one can know anything about God.
Do you know that about God? To assert that God is unknowable, is to say a lot about God.

Some will rest their case against God using logic, Mathematics/Science.

• All I believe in are the laws of logic.
Is that statement one of the laws of logic? (NO)

• We can only discover truth by testing and experimentation.
Are you able to test that assertion? (NO)

• Apart from mathematics, we can know nothing for sure.
Is this part of a mathematical equation? No. Then what you’re saying, is the very basis to reject what you say.

• All knowledge comes from observation.
Have you observed ALL knowledge? The assertion does not make possible its own ground of proof.

• All English sentences consist of four words.
This sentence comments on all English sentences, including itself. It fails to meet its own demands, hence it is false.

• The only genuine knowledge is obtained by sciences.
Is that proposition verified by sciences? No. Then it self-destructs. It saws off the limb it rests on.

• We can know nothing about reality.
Do you know that about reality?

• Nothing can be known.
Do you know that? Some skeptics argue that “nothing can be known.” Can that STATEMENT itself be known?
If so it refutes itself, if not, one may not even know that which the statement asserts.
Skillful skeptics often attempt to make an exception for the statement itself revealing the inconsistency of the statement itself.
….

From the book; “Relativism, Subjectivism, and Self-refuting Statements Defeated.”