From the perspective of structural ontology, phase cells are taken as the basic units for describing structure in statistical mechanics. Within this framework, the relationship between a system’s temperature and the distribution of energy within phase cells is one of representation and being represented; that is, temperature is a statistical representation of the system’s energy distribution. Consequently, the photon number in a thermal radiation field has statistical significance, and whether it is conserved is not a question that needs to be decided; thermal excitation, in a statistical sense, represents the redistribution of energy within phase cells.