The author’s main concern is to promote understanding of the basic ideas underlying switching theory. Nothing is taken for granted, whether it is the concept of a logic variable, that of feedback in a latch or sequential circuit, or the necessity to encode internal states. This very basic and thorough approach enables the development of new concepts such as Composition, or Verification. The theoretical side is enhanced by using predicate (instead of propositional) logic allowing for formal proofs till now unattainable. On the practical side, sequential circuits that hitherto were obtained intuitively are now open to a formal synthesis procedure.