The person can deny oxygen exists, but the effect on a human can still be observable. A person can deny the need for a god to have logic, but the same need for a god won’t be observable. There is no world where the There are other, more evidence based, explanations available, unlike with oxygen for respiration. Development of the brain within species through time is perfectly acceptable for a greater ability to reason and no god is required.
We don’t need to invoke deities to explain why humans can use their brains to put two and two together or why we can expect a certain outcome from an action.
