In this book the reader will find expounded a method of investigating nature by means of which scientific understanding can be carried across the boundaries of the physical-material to the supersensible sources of all natural events, and thereby into the realm where is rooted the true being of man. The beginnings of this method were worked out by Goethe more than 150 years ago. The nineteenth century, however, failed to provide any fertile ground for the development of the seeds thus sown. It was left to Rudolf Steiner, shortly before the end of the century, to recognize the significance of 'Goetheanism' for the future development not only of science but of human culture in general. It is to him, also, that we owe the possibility of carrying on Goethe's efforts in the way required by the needs of our own time.