When a physical system is complex it may possess a behaviour that displays some similarities with true living systems. If we consider, for instance, an enzyme reaction involving the random binding of two substrates A and B to the active site of the enzyme, the correct manner to study this reaction is to derive the rate equation as a combination of elements in interaction, namely the free enzyme E and the two enzyme-substrate complexes, EA and EB. In addition to these steady state concentrations there are local circuits of E, EA and EB. These circuits can be modified by the global system itself in such a way that, for pure physical reasons, the system can favour, for instance, a circuit running to E, to EA or to EB. These circuits exist and their functioning can be modulated by the system considered as a whole.