Abstract
This paper aims to raise awareness of the necessity for the teaching of the axiomatics of physical systems in circuit theory. It is shown how SI base and derived quantities can be regarded as undefined and defined terms of the theory and that Maxwell's equations require four, however, lumped circuits and lumped mechanical and thermal systems require three base quantities. Attention is drawn to the fact that through and across variables and time can be regarded as the three base quantities for each physical domain, and the two Kirchoff's laws, expressed in the through and across variables, as the two axioms. An alternative set of three base quantities, i.e., energy, through (across) variable and time, is proposed for lumped systems. The axiomatization of physical theories, which involves the determination of the undefined terms and laying down the axioms, is discussed.