The influence of Gottfried Wilhelm Leibniz on the Psychology, Philosophy, and Ethics of Wilhelm Wundt

Gottfried Wilhelm Leibniz (1646 - 1716) is regarded as the most important German philosopher and uni-versal thinker between scholasticism and Immanuel Kant. Wilhelm Wundt (1832 - 1920) was a neurophys-iologist, psychologist and philosopher. He is internationally known as the founder of experimental psy-chology and the first to build a laboratory with an explicit research program. Leibniz’s essential influence on Wundt’s thinking, so far, is not thoroughly examined. In the preface to his Grundzüge der physiologischen Psychologie, Wundt refers to Immanuel Kant and Johann Friedrich Herbart being the most influential in shaping his philosophical standpoints. Taking this lead, however, it is noticeable that Wundt’s attitude is mostly critical, especially regarding Herbart. In comparison, Leibniz’s impact is essential and constructive in forming Wundt’s psychology, philosophy, epistemology, and ethics. This influence is obvious in Wundt’s essay on Leibniz in 1917 and from a number of basic concepts, terms, and epistemological principles in Wundt’s work. Furthermore, Leibniz’s perspectivism was forma-tive to Wundt’s cognitive style. The present contribution refers to four basic postulates in Leibniz’s thinking: the Law of Continuity, the Principle of Harmony, the Principles of Individuality and of Autonomous Activity; and the main part in-cludes 10 issues or sections: (1) Monads and the mind (soul): substance and actuality; (2) Epistemology: psychologically-reflected idealism – as opposed to sensualism (empiricism); (3) Parallelism: psychophysical and harmonically pre-stabilized correspondence; (4) Perception and apperception; (5) Consciousness, self-awareness and individuality (the person); (6) Striving and appetite, volition (the will), intellectualism and voluntarism; (7) Principles of sufficient reason, principles of causality and purpose, unity and plurality, perspectivism; (8) Concepts of development (evolution); (9) Ethics and the idea of humanity; (10) Mon-ism. The sections include citations from Leibniz’s work, Wundt’s direct commentaries on Leibniz, as well as further citations from Wundt’s work referring to epistemology and indicating consequences for research and methodology. Obviously, Leibniz had a profound impact on psychology and philosophy as conceived by Wundt who transformed philosophical concepts to an innovative research program and an advanced methodology in the formative years of modern psychology. The seminal ideas, however, had little resonance, at least not a permanent impact on theoretical or empirical psychology as understood by Leibniz and by Wundt. In summary, it can be said that in German and English-language historiography of psychology (apart from very few voices) there are astounding and radical breaks in tradition with regard to Leibniz’s philosophical psychology and Wundt’s philosophically reflected empirical psychology. This essay is a plea for a renewed discourse on philosophical presuppositions in psychology and, thus, complements previous books: Mensch-enbilder (2007), Wilhelm Wundt – Pionier der Psychologie und Außenseiter? (2011), Zur Kategorienlehre der Psychologie (2013), Theoretische Psychologie (2015a).