- Making a positive claim that there is a God is assuming knowledge not justified. This is the "God of the Gaps" argument.
- Making a positive claim that all reality is natural is assuming knowledge not justified. This is Philosophical Naturalism.
- Saying "We don't know" to a claim that can't be falsified is Methodological Naturalism and is a major feature of the scientific method. Let's not give the theist any evidence of faulty reasoning.
Click on this link for more on Methodological Naturalism. The burden of proof is on the one making the claim. Don't make claims that cannot be supported.