This article explains the reason of existence of interpreting theory. Although it is true the Phoenicians managed indeed to sail without a compass, no modern mariner would dream of putting to sea without one. What is the compass of interpreters and teachers? The answer is a general theory of mediated interlingual intercultural communication that will constantly point to the communicator’s north: relevant perceptual identity between meaning as meant by the speaker and meaning as comprehended by the addressee(s). In order to explain what is meant, the author briefly visits the model of communication developed by García Landa and the author himself.