The point that the impermanence of laws, whether natural or social, must be accounted for has been overlooked by Marxist-Leninists. They assume that it is enough to appeal to the change of social conditions — and these do change constantly — to account not only for the restricted applicability but also for the transitoriness of laws themselves, the "disappearance' of the "old' and the "emergence' of the "new' laws. This, however, is not the case. Suspicions have been aroused that there is something fundamentally wrong with the otherwise plausible view that the laws of economics are historical in character, limited to certain conditions of time and space ⁵³. In Poland it was Lange who realised that the point in question required elucidation and who tried to till the gap in the theory by some provisions, which, without giving up the historical character of socio-economic laws, would account for the continuity of the evolutionary process.