With the wide sweep of Moslem conquest another element came into the development. This was Roman law, which the Moslem jurist found at work in the conquered Roman provinces and in the law courts of which they went to school. It is to be remembered that the Arab armies were not devastating hordes; they recognized the need of law and order wherever they went, and it was the policy of their leaders to take over the administrative systems of the countries which they seized. Even the Arabic legal nomenclature shows evident signs of literal translation from Latin, and many Moslem principles can be traced to the Roman codes. One important development was plainly influenced by the liberty involved in the _Responsa prudentium_ of Roman lawyers, and by the broad conception of the law of nature in the Edict of the Praetor. In its earliest stages Moslem law recognized in the judge a liberty of opinion (_ra'y_) which went beyond even that of the _Responsa_ and became plain equity, in the English sense, and one school (the Hanifite) established as a basis the right of preference (_istihsan_) even when the analogy of the code dictated otherwise; while another (the Malikite) used the term _istislah_, "a seeking of (general) benefit" to the community, in a similar situation. But these developments were bitterly contested, and the liberty of opinion was in the end narrowed down to a principle of analogy (_qiyas_), the nearest approach to which in Western law is legal fiction. It is necessary now to return to the first successors of Mahomet. "For thirty years after my death," he is said to have declared, "my people will tread in my path (_sunna_); thereafter will come kings and princes." This tradition crystallizes the later feeling of Islam. The first thirty years were a golden age; the centre of the state was the Prophet's own city of Medina; the conditions of the state continued in close conformity to those of his own time. The study of tradition, i.e. of his usage, went hand in hand with the study of law. They were vital functions of the state, and it encouraged both.