The earliest doctoral degrees (theology – Divinitatis Doctor (D.D.), law – Legum Doctor (LL.D., later D.C.L.) and medicine – Medicinæ Doctor (M.D., D.M.)) reflected the historical separation of all higher University study into these three fields. Over time, the D.D. has gradually become less common outside theology and is now mostly used for honorary degrees, with the title "Doctor of Theology" being used more often for earned degrees. Studies outside theology, law and medicine were then called "philosophy", due to the Renaissance conviction that real knowledge could be derived from empirical observation. The degree title of Doctor of Philosophy is a much later time and was not introduced in England before 1900. Studies in what once was called philosophy are now classified as sciences and humanities.