An attempt to define the pastoral as a genre poses the problem that the term is highly ambiguous as applied to a vast range of literature . Works classified as pastoral may differ in form, subject matter, and cultural references such as religion or mythology . The shepherd’s songs of Theocritus, the Eclogues of Virgil, the Elizabethan dispraise of court life, and Milton's elegy for Edward King arc all classified as pastorals. It becomes necessary to suggest, as does W.W . Greg, that the basic quality of the pastoral is determined not by the fortuitous occurrence of certain established characteristics, but by the fact that the pieces in question are based more or less upon a philosophical conception which undergoes modification through the ages, but bears evidence of organic continuity.