How do we know what rights we have? Hmmm.
How do we know how many planets there are? By scientific investigation. Various theories were attempted at explaining the universe and currently we have a model that includes probably 10 planets in an heliocentric solar system.
What rights do we have? We can know by scientific investigation. The courtroom is our labratory, and judges are the scientists in a common law system. Such an arrangement existed in England off and on for several hundred years. The development of good law coincided with the development of good science. Now both are failing.
Common law got far enough to determine that life, liberty, and property are three of our inherited rights. It answered a lot of questions. But the system was destroyed before it could answer others.
So, whether Murray Rothbard is God or not, we know that we do have certain rights as a law of nature.