Yet, notwithstanding the divisions of the Muhammedans and the immense distances separating them, a unity not only religious but also intellectual was maintained. The Muhammedans learned rapidly from the peoples they conquered and established for the diffusion of learning a sort of university system of travelling scholarships. Aided by Arabic as the universal language of learning, students journeyed from teacher to teacher, from the Atlantic to Samarcand, gathering hundreds of certificates. The education was designed to turn out theologians and lawyers; but theology included studies in metaphysics and logic, and the canon law required a knowledge of arithmetic, mensuration, and practical astronomy. Technical education was maintained by gilds who perpetuated the “mysteries” of the craft through a system of apprenticeships. And it is to be noted that there was no distinction made between so-called arts and so-called crafts. The gild-system covered all kinds of constructive work from engineering to the making of a needle, and if the work permitted elements of beauty and decoration these were, as a matter of course, included. Hence the proficiency and inventiveness and exquisite perfection of workmanship displayed by the Muhammedan craftsmen. But their Koran enjoined a literal obedience to the Mosaic law against “the making of any graven image, or the likeness of anything that is in Heaven above or in the earth beneath or in the waters under the earth.” Accordingly, there were no sculptors or painters in the full sense of the term; only decorators of moulded, engraved, or coloured ornament, the motives of which were confined to conventionalised flower and leaf forms and to geometric designs of practically endless variations of the straight line and curve, in meander, interlace, and fret, into which they often wove texts from the Koran or the sacred name of Allah. It is to these designs by Arab artists, influenced to some extent by Byzantine, that the term _arabesque_ was first applied. Meanwhile it was the practice of Muhammedanism to absorb as far as possible the traditions of each nation it conquered. Gradually, therefore, the strictness of its orthodoxy was modified. In Persia, for example, the representation of animals was permitted in the arts of design, and the representation of human beings followed. Similarly, the architectural style of each locality was affected by the previously existing architecture. The examples which remain are chiefly of mosques, tombs, houses, and palaces.