"Külpe and Marbe have shown psychological research in Würzburg a certain, distinctive and trend-setting line. The gray theory was forced to deal with [the facts] of life and experience and to test itself on them. Just by this the theory gained inner firmness and validity. [...]
For the future we must strive for a harmonious balance between theory and practice, if we as psychologists do not want to theorize and terminologize apart from reality and if, on the other hand, we do not want to be swallowed up by the interests of practice."
W. Arnold on the occasion of the opening ceremony of the new institute in Domerschulstraße 13 on 13.1.1956