It doesn't matter what he referred to himself as. That was his practice.
This country was founded on the belief that right are inherent. This isn't even really a belief as it is demonstrably true; if you lived by yourself on a deserted island, you could do whatever you pleased. Rights can only be limited by people, and thus the inherency of rights is fact- not belief. Any question about why rights are inherent is pure speculation; we only can know for certain that they are.