As culture evolves gradually, respective characteristics increase and decrease in frequency and strength. This makes the definition of a period necessar ily fuzzy with respect to space- time, but it makes the periods themselves not less real or objective. Rather, spatiotemporal bounds make no sense beyond a certain degree of precision. Further, culture evolves in many directions at the same time. The degree of synchronization between different kinds of phenomena, such as style and political system, may vary considerably. This gives raise to multiple points of view. Necessarily, such views differ objectively in their spatiotemporal bounds. Finally, archaeological observation is restricted to the products and traces of some of these phenomena. The degree to which these are correlated to the non-observable phenomena, gives raise to subjective interpretations. Jean-Claude Gardin (Gardin 1990) analyzes this process in general terms.