Determinism and Causality

From Schlick’s point of view, the task of Philosophy of Nature is not to decide about the validity of the causality principle, but to elucidate its meaning, by reducing causality to « nomicity », thus by defuning causality in Humean terms, as a mere regularity. But the only way both to save necessity and to define it by universality would be to identify it, somehow, to a necessary universality. And the price for abandoning the causal axiom (even if it cannot be seen as a necessary presupposition) would probably be too high.