  As Tarski says, the idea of understanding the notion of logical consequence by means of the notion of truth preservation on all interpretations is not an original idea of his, but one implicit in the logical and mathematical practice of his time (especially among mathematicians interested in offering independence proofs). What is new to Tarski’s proposal is that he makes precise the idea using the apparatus he had developed for the mathematical characterization of satisfaction and truth. He does not give a detailed example, but it seems reasonably clear how he would proceed from the indications he gives in (1936a), (1936b) and (1937).