I find it curious that the discussion seems centered not on the nature of the Earth but the validity of the individual mind to know it.
Logic is a predicate for truth. Truth takes the form of sound, rational statements (note: root word of 'rationale' is 'ratio'). Truth, as it is relevant to us, does not exist outside of these rational statements. Accordingly, truth should be modeled in terms of the mind as it relates to the rest of reality.