epistemology and ethics – the two fundamental areas of philosophy." Wundt's concepts were developed during almost 60 years of research and teaching that led him from neurophysiology to psychology and philosophy. The interrelationships between physiology, philosophy, logic, epistemology and ethics are therefore essential for an understanding of Wundt's psychology. The core of Wundt's areas of interest and guiding ideas can already be seen in his Vorlesungen über die Menschen- und Tierseele (Lectures on Human and Animal Psychology) of 1863: individual psychology (now known as general psychology, i.e. areas such as perception, attention, apperception, volition, will, feelings and emotions); cultural psychology (Wundt's Völkerpsychologie) as development theory of the human mind); animal psychology; and neuropsychology. The initial conceptual outlines of the 30-year-old Wundt (1862, 1863) led to a long research program, to the founding of the first Institute and to the treatment of psychology as a discipline, as well as to a range of fundamental textbooks and numerous other publications. Physiology During the Heidelberg years from 1853 to 1873, Wundt published numerous essays on physiology, particularly on experimental neurophysiology, a textbook on human physiology (1865, 4th ed. 1878) and a manual of medical physics (1867). He wrote about 70 reviews of current publications in the fields of neurophysiology and neurology, physiology, anatomy and histology. A second area of work was sensory physiology, including spatial perception, visual perception and optical illusions. An optical illusion described by him is called the Wundt illusion, a variant of the Hering Illusion. It shows how straight lines appear curved when seen against a set of radiating lines. Psychology Starting point As a result of his medical training and his work as an assistant to Hermann von Helmholtz, Wundt knew the benchmarks of experimental research, as well as the speculative nature of psychology in the mid-19th century. Wundt's aspiration for scientific research and the necessary methodological critique were clear when he wrote of the language of ordinary people, who merely invoked their personal experiences of life, criticized naive introspection, or quoted the influence of uncritical amateur ("folk") psychology on psychological interpretation. His Beiträge zur Theorie der Sinneswahrnehmung (1862) shows Wundt's transition from a physiologist to an experimental psychologist. "Why does not psychology follow the example of the natural sciences? It is an understanding that, from every side of the history of the natural sciences, informs us that the progress of every science is closely connected with the progress