the four elements: earth, water, fire, and wind (Buddhism)
the four freedoms: speaking out freely, airing views fully, holding great debates, and writing big-character posters, 大鳴大放|大鸣大放[dà míng dà fàng], 大辯論|大辩论[dà biàn lùn], 大字報|大字报[dà zì bào] (PRC)