Ross's Kritik der sogenannten praktischen Erkenntnis pertains more to moral philosophy than to the philosophy of law, even if its contents are important for the latter, too. Its main objective is to show the theoretical groundlessness of any evaluative judgment. This happens when Ross takes the behaviourist approach of reducing psychology to physiology, which opens up fruitful comparisons with Marxist materialism, and in particular with that of Georges Politzer. Another fundamental question concerns the assumption that theoretical nihilism would lead to practical nihilism, as argued by Theodor Geiger (but denied by Ross). And yet, if Geiger is right, can this have no effect on people's everyday lives?