Between the mid-1920s and early 1930s in Germany, there was a strong interest in the study of synesthesia, understood as an experience that involves multiple senses simultaneously and emphasizes the unity of sensory perception. This interest extended across diverse fields, including art, philosophy, science, and music. For instance, Vassily Kandinsky believed in the possibility of “hearing with the eyes” and translating musical experiences into colors. Authors from the Gestalt tradition actively engaged in this debate. In 1925, Erich von Hornbostel argued for the existence of genuine multisensory experience, contrasting with more rigid perspectives held by others. Wolfgang Köhler studied how certain words, such as “rough” or “sweet,” reflect an isomorphism between different sensory experiences and developed the famous Maluma-Takete experiment, which demonstrates how shapes and sounds can be non-arbitrarily associated. Heinz Werner, influenced by Gestalt psychology, employed a genetic-comparative approach that integrated anthropological, psychopathological, and developmental research to advocate for an original unity of the senses. Kurt Koffka, reflecting on the intermodal metaphors consistently present in everyday language, also drew on the ideas proposed by Werner. Other researchers, including Kurt Goldstein and Wolfgang Metzger, explored the expressive and intermodal qualities of colors, linking the perception of warm and cool colors to bodily posture and sensorimotor responses, and highlighting that some sensory qualities are supramodal—manifesting not only across sensory domains but also in human behavior. The Gestalt tradition thus sought to demonstrate that synesthetic experiences are not mere rhetorical devices, but reflect a genuine unity and interconnection among the senses, challenging the strict separation of sensory modalities established by Johannes Müller’s law of specific nerve energies. These ideas profoundly influenced philosophers such as Merleau-Ponty, who adopted and further developed these themes.