The naming of degrees eventually became linked with the subjects
studied. Scholars in the faculties of arts or grammar became known as
masters, but those in philosophy, medicine and law were known as
doctor. As study in the arts or in grammar was a necessary
prerequisite to study in subjects such as philosophy, medicine and
law, the degree of doctor assumed a higher status than the master's
degree. This led to the modern hierarchy in which the Doctor of
Philosophy (Ph.D) is a more advanced degree than the Master of Arts
(M.A.). The practice of using the term doctor for all advanced degrees
developed within German universities and spread across the academic
world.

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