In nature, there are predators and prey, carnivores, herbivores and omnivores. There are some where males fight to the death to establish dominance over a troop.
Some libertarians talk about “natural rights” when talking about humans.
It is my belief that natural rights are a logical extension of the obvious and natural differences between humans and animals. The atheist libertarians that have most articulated the philosophy, for the most part, have extrapolated the NAP (and other axioms and conclusions) from those differences, and respective characteristics, to get to “natural rights” ideas.
From my perspective, Austrian economics is the best example of the application of eternal principles articulated in the Bible, even the 10 Commandments. Atheists and agnostics reject the 1st Commandment but are still responsible for living up to at least the NAP as a logical “corollary” of the NAP.
But nature operates according to certain rules, with scientific disciplines purporting to be about teasing those rules out from observations of nature.
But you cannot define nature as a coherent entity with creative powers. The law of entropy is an axiomatic principle that recognizes that nature acts in the way described. Nature has no independent agency and cannot overrule itself.
But human agency can. Some may say there is no free will, but ask one if he can change his mind if he wants to. He might say no, but many of them have changed their mind. Most physicists acknowledge quantum fluctuation, for example, and the “uncertainty principle”.
But now atheists that recognize principles of Austrian economics and how the free market works better than other economic models in human society, also have to explain why the NAP that is necessary for a true free market, does not work for ants.
“They’re not human” is an obvious answer, but when you ask them why humans are different they have to fall back on non-theistic answers that do not really explain it, if humans came to be through the same processes as ants.
So what is the essence in nature that requires natural rights?
My answer is that there has to be an “intentional agency” that made the rules. The rules that nature has not choice but to live by, and the rules that are implied by how human societies work best. Even an atheists like Mises and Rothbard have deduced a corollary of “the law of love” as the minimum rule for society to work in a way that is the optimum best for the aggregate, the NAP: no one person supplanting another’s volition by force, coercion, or fraud.
To sum it up, even atheists who subscribe to the NAP are able to deduce certain principles from certain axioms of human action, rules that explain how nature actually works in human society. It can even explain what happens when some humans violate the NAP.
They start from nature. But nature also has rules and Mises started from scratch from those rules in “Human Action” to derive how human societies and economics actually work.
But looking at nature, you can also make certain sure deductions. The laws of entropy, for example, there is no law of nature that any branch of science has been able to come up with an explanation as to why the laws of entropy and the strong anthropic principle can be universal rules for the cosmos without being able to deduce that there is an intelligent agency to engineer it, with the power to create it.