By Muslim scholars of the 10 th century the sciences were divided into ‘Arab Sciences’ and ‘Old’- or ‘Non-Arab Sciences’. To the former belonged Grammar, Ethics and Dogmatics, History and Knowledge of Literature; to the latter Philosophy, Natural Science and Medicine. In the main the division is a proper one. The last-named branches are not only those which were determined the most by foreign influences, but those too which never became really popular. And yet the so called ‘Arab Sciences’ are not altogether pure native products. They too arose or were developed in places in the Muslim empire where Arabs and Non-Arabs met together, and where the need was awakened of reflecting on those subjects which concern mankind the most,—Speech and Poetry, Law and Religion,—in so far as differences or inadequacies appeared therein.