Existence is.
Consciousness observes existence.
Identity is...I am me, and you are you.
It's possible for humans to differentiate true from false.
These are some examples of self-evident claims. They are accepted as true in the argument, even if you reject them.
Natural rights...probably self-evident too.
As a shared observation, most people are aware of their instinct for survival. This gets codified as "right to life" when making up rules for society..it stems from our shared desire to live, and to see those we love and depend on live..and by extension we can imagine everyone feels the same (within reason).
But there's more to it. We do not have a survival instinct by accident, it resulted from it being an overall a better survival trait than without. And such things can be modeled in mathematics. Game theory has examples of such social interactions, potential rules and outcomes. When fairness, can be quantified, and trust...tit for tat, etc., it appears those rules are the case whether we believe them, or not. There's a gulf of work that has to be done to bridge the two (if it's even logically possible entirely), but there is enough there that it seems to be the case.
So these rules of game theory, that predict outcomes, we did not create them, we discovered them. And evolution also discovered them, and coded them into our DNA.