Rector at Upton-upon-Severn from 1553, Dee was offered a readership in mathematics at Oxford University in 1554, which he declined, citing as offensive English universities' emphasis on rhetoric and grammar (which, together with logic, formed the academic "trivium") over philosophy and science (the more advanced "quadrivium", composed of arithmetic, geometry, music and astronomy). He was busy with writing and perhaps hoped for a better position at court. In 1555, Dee joined the Worshipful Company of Mercers, as his father had, through its system of patrimony.