  Even though the words are arbitrarily imposed (whence arise the differences between all languages), the modes of signifying are uniformly related to the modes of being by means of the modes of understanding (whence arise the grammatical similarities among all languages). Focusing on the terms of ‘sign’ and ‘signification’, speculative grammar, as a science of general cognitive-linguistic structures, prescinds from all the different national languages — and even from vocal language as such. For it is, as Martinus Dacus points out, not essential for speculative grammar to deal with vocal expressions or with structures of vocal sign systems, because any kind of signs could be the object of the considerations of a modist grammarian. The fact that he is concerned with linguistic signs rather than with gestures or the “language of eyes” is only due to the fact that vocal expressions are, compared to other kind of signs, more apt for human communication.[38]