In the early 20th century there was a new surge of activity in Scottish literature, influenced by modernism and resurgent nationalism, known as the Scottish Renaissance. The leading figure in the movement was Hugh MacDiarmid (the pseudonym of Christopher Murray Grieve). MacDiarmid attempted to revive the Scots language as a medium for serious literature in poetic works including "A Drunk Man Looks at the Thistle" (1936), developing a form of Synthetic Scots that combined different regional dialects and archaic terms. Other writers that emerged in this period, and are often treated as part of the movement, include the poets Edwin Muir and William Soutar, the novelists Neil Gunn, George Blake, Nan Shepherd, A. J. Cronin, Naomi Mitchison, Eric Linklater and Lewis Grassic Gibbon, and the playwright James Bridie. All were born within a fifteen-year period (1887–1901) and, although they cannot be described as members of a single school they all pursued an exploration of identity, rejecting nostalgia and parochialism and engaging with social and political issues. This period saw the emergence of a tradition of popular or working class theatre. Hundreds of amateur groups were established, particularly in the growing urban centres of the Lowlands. Amateur companies encouraged native playwrights, including Robert McLellan.