It will first of all be clear that not only incompatible but also compatible characters can be thought in emptily intended combinations. This indeed … - Christian von Ehrenfels

For the intimate fusion of touch, temperature and sometimes also taste and smell sensations into a single unified total impression raises the question of whether we do not have here Gestalt qualities which are built up upon a foundation belonging to several sensory regions. As can easily be recognized, it is just as possible that a complex of, say, touch and temperature sensations should provide the foundation for a Gestalt quality as should a complex of sound sensations. Indeed no a priori objection can be raised even against the idea that there should exist sound-colour-Gestalten spanning the data of the senses of sound and vision as something like a bridge - even though we do not believe that we can detect anything of this sort in sensation.

By a Gestalt quality we understand a positive content of presentation bound up in consciousness with the presence of complexes of mutually separable (i.e., independently presentable) elements. That complex of presentations which is necessary for the existence of a given Gestalt quality we call the foundation [Grundlage] of that quality.

We must also accept the possibility of Gestalt qualities comprehending complexes of elements of different categories.