wrote to a colleague, however, that the concepts behind the book were, “the source of the investigations in the psychology of thinking.” So, he had anticipated the idea of imageless thought in this publication. Külpe was still under the shadow of Wundt during this time. In fact, only one of his distinctive views was included, which was his criticism of the subtractive procedure on reaction time. Two years later, Grundriss der Psychologie was translated into English by Edward Titchener under the title Outlines of Psychology. In 1897, Külpe published a handbook called Introduction to Philosophy. This book was a guide to both past and present philosophy at the time, and a basic text for German university students of not just general philosophy, but psychology, logic, ethics, and aesthetics as well. In the book, Külpe also looks at the relations of the body and the mind, and in doing so, takes a dualistic position. Külpe also gives a clearly describes the relationship between physical and psychical, or in other words natural science and psychology. He identifies the possibility of what he refers to as a mind substance. He theorized that both matter and mind are abstractions from thought experience. He believed that if matter required the idea of substance, why would mind not require substance as well. The book is less than 350 pages and went through seven editions and four translations, including into English by W.B. Pillsbury and Titchener under the title Introduction to Philosophy. In 1912, Külpe published Über die moderne Psychologie des Denkens, which translates into English as On the Modern Psychology of Thinking. In this book, he was looking back upon his focus on the systematic experimental introspection method. He believed that before systematic experimental introspection existed, research on thought was incomplete. He also believed that having the subject report only on sensations, feelings, and presentations in thought research was severely limiting in that it did not provide an acceptable opportunity to identify what could be considered neither sensation, feeling, nor presentation. Once they were given the opportunity to objectively self-observe and describe what was neither sensation, feeling, nor presentation, yet was still a thought process; Külpe and his colleagues identified the need for new definitions and concepts aside from those that already exist. As Külpe wrote: “The subjects began to speak in the language of life and assign less importance to the presentations for their inner