This introduction presents an overview of the key concepts covered in this book. The book provides two related sets of ideas, programmed instruction, and the so-called 'systems thinking'. It sets out to show that, with these two clusters of ideas, it is possible to pick one's way through the minefield of the training world, and to take an informed and critical position on any problem or technique. The whole field of training is in a rapid state of change. New needs, new techniques, new people entering the field, all contribute to the ferment. With all this, there is no generally accepted scheme which unifies the whole of what is known about training, and sets out principles which are equally applicable to operator training and to management training. The book is an attempt to provide such a framework.