The cantata "Rejoice in the Lamb" was written "to order" for the fiftieth anniversary of St. Matthew's Church in Northampton, one of Britten's many community-oriented commissions, which he always took very seriously. The text, by late-eighteenth-century poet Christopher Smart, is unusual in several ways. Smart's ecstatic celebration of his cat Geoffrey as a vessel of the Lord is rather eccentric, to say the least. Things get even stranger as Smart offers a homily on the spiritual values of Geoffrey's hereditary enemy, the mouse. Eventually, Smart starts blessing everything in sight, including letters of the alphabet. Later in his life, Smart was plagued with mental illness and institutionalized. Britten, however, takes Smart's bizarre, pantheistic ramblings at face-value, perhaps finding a bit of beauty in the madness.