"This book is intended primarily as a textbook for advanced students of psychotherapy. It will not be difficult for the representatives of this professional group, who have often enjoyed different training, to apply the reports on Transactional analysis to their own conceptual systems. No doubt lay people will read this book, and that is why I have written it so that they too can understand it. In conventional psychotherapy, three different levels of terminology are usually used: that of therapists among themselves, that between therapist and patient, and that of patients among themselves. They differ from one another in the same way as ancient Greek differs from modern Greek. If the differences are eliminated as far as possible in favour of a vernacular language, this increases the 'communication possibilities'.