In the history of music there are seldom as rapid musical developments as we can find in Scriabin's works. In only 31 years Scriabin made a breathtaking development: in his early works he still uses a romantic tonal language, while his later works are far-reaching into the 20th century. Scriabin's development is gradual and consequent, each step can be derived from the preceding, thus connecting the music of the 19th and 20th centuries. He can be regarded as a key composer of his age.Harmony is the central factor in Scriabin's musical thinking. From harmony everything else is developed. It defines the form, also the melody and tone systems are developed from it.This book is concerned with the following basic issues: Which elements in Scriabin's harmony are new, and what has been derived from the tradition? Why is the development in Scriabin's works consequent, once started, why did it have to follow a certain course? Is there something elemental in Scriabin's way of thinking that pushes ahead this development?