The empiricists claim that since knowledge can only come from the senses and there is no sensory information about God, knowing anything about God, including God’s existence is impossible.
However, theists have made number of responses to this, the first of which focuses on Ayer’s Verification Principle.
Ayer argued that religious language was meaningless as it could not be verified, but the Verification Principle itself cannot be verified, so surely the Verification Principle is meaningless! You can’t use a meaningless principle to argue that something else is meaningless.
Next, theists might point out that the empiricists’ demand for evidence of God can be met with reference to the cosmological and design arguments. The Cosmological Argument starts with observational evidence of, for example causation, and argues that therefore there must be a first cause. The Design Argument starts with evidence of the complexity of the world and argues that there must therefore be a designer. Additionally it might be argues that religious experience is a form of evidence as without a natural explanation maybe these experiences point us to a supernatural explanation.
While none of these prove that God exists, they can be seen as evidence, which is what the empiricists are demanding.
Furthermore, theists might argue that empiricism is itself a flawed idea. Clearly we can obtain knowledge from our senses, but there are many instances when knowledge goes beyond this. Our knowledge is not limited to our senses. The beliefs we hold about a particular piece of music or a beautiful view cannot be explained solely in terms of what we hear or see. There are deeper levels to us and for theists, religious truth operate at these deeper levels of experience rather than at our sensory level.
In summary, theists argue that empiricism only gives a partial explanation of where knowledge comes from. Ayer’s Verification Principle and limits of empiricism should us that knowledge has other sources than just the senses.
Theists would also argue that there is evidence of God all around us in creation.