We have thus brought forward evidence to show that episcopal schools existed at Canterbury, York, and Hexham, and that advanced instruction was available at these centres. The general hypothesis we submit is that the cathedral city of each diocese became gradually recognised as a place of higher education, and that it was commonly regarded as the duty of the bishop to provide, either personally or by deputy, such higher education as the circumstances of the time rendered possible. Facilities would also be required at these centres for elementary instruction, and also for instruction in the "specialist" art of writing. As the demand for such instruction arose, so the Church endeavoured to meet it, and classes were established for this purpose. Thus, in a letter written c. 796 by Alcuin to Eanbald II. Archbishop of York, he recommends that separate masters should be appointed to teach those "qui libros legant, qui cantilenae inserviant, qui scribendi studio deputentur."[69] With the spread of Christianity in this country, the parochial system originated. For this purpose, the Saxon "tun" was taken as the unit of ecclesiastical organisation and it became known as the "parish," the specific area placed under the spiritual over-sight of the parish priest. We must again remind ourselves that Latin was the language of the Church, and that to participate in the worship offered by the Church, to join in its psalms, to understand its doctrines properly, or in fact to become in any sense of the word a "churchman," a knowledge of Latin was imperative. A custom naturally arose that the parish priest should keep a "school of grammar," or, as we should term it to-day, should hold a Latin class for those who were desirous of learning that language. In course of time this custom became obligatory and a part of the law of the Church. Thus, at the Council of Vaison held in 529, it was decreed that each priest, who was in charge of a parish, should also have at his house a class of young men for the purpose of preparing them for the sacred ministry. These young men were also to be engaged in teaching the small children. The bishop in his visitation of the parish made enquiries as to whether this law was carried into effect.[70] The enactment of Vaison was repeated by subsequent decrees of the Church, notably by that of Tours, and the establishment of schools of grammar to be taught by the parish priest was a definite part of the system of the Church.[71] This requirement was reiterated from time to time. Thus Theodulf of Orleans, the coadjutor of Alcuin in carrying out the educational reforms of the kingdom of Charles the Great, issued a letter to his clergy in 797 in which he reminded them that "Presbyteri per villas et vicos scolas habeant, et si quilibet fidelium suos parvulos ad discendas litteras eis commendare vult, eos suscipere et docere non renuant."[72]