The search for universals is a tendency which is based in the structure of human knowledge and which correlates with a complementary search for individual properties. The recurrence to universals is inherent in both classificatory and deductive knowledge. Admittingly, the attempt to classify the definitorial universals of human language hierarchically meets various difficulties. In contrast to the universals of the formal systems of logic and mathematics, the universals of human language are of a heterogeneous character. Often the relation among the universals of language is not to be determined merely as a relation of logical compatibility or implication, but, additionally, as a relation of means and end. Not everything which is logically possible according to certain basic universals of language is also realized by the languages. Beyond the logical possibilities linguistics must recognize structural, perceptual and cognitive restrictions. – Universal properties have the merit that they are, presumably, more fundamental in the language system than the mere particular properties. – One of the important discoveries of the more recent investigation in language universals is that diversities, in particular certain types of interlingual inversions and gradual distinctions in the development of a dimension, are also subject to universal laws. – As a motive for research in language universals, which is also a motive for the opposed inquiry in linguistic relativity, one must ultimately consider a psycho-sociological factor. According to the level at which one seeks identification with a gruppe (ethnocentric or anthropocentric) one will be more likely to advocate a constrative linguistics (in the broadest sense of the term) or a universal linguistics.