The assumption that there exists a common grammatical core which is valid for all languages and which can be determined by a priori insight is an old and venerable speculation of both linguists and philosophers. This assumption is not fashionable any more, and the old arguments adduced for it could not withstand the onslaught on the empirical evidence provided by the study of "exotic" languages. Nevertheless, in a certain sense, to be more closely determined later on, it has been taken up by no less a man than Rudolf Carnap, one of the leading logicians and anti-speculative philosophers of our time.