At first , a talk given March 6 , 1927 at Battersea Town Hall , at the South London Branch of the National Secular Society . It was published that year as a pamphlet and was later published , with other essays , in the book , Why I Am Not a Christian : And Other Essays on Religion and Related Subjects ( ISBN 0-671-20323-1 ) . Originally a talk given March 6 , 1927 at Battersea Town Hall , under the auspices of the South London Branch of the National Secular Society , it was published that year as a pamphlet and was later published , with other essays , in the book , Why I Am Not a Christian : And Other Essays on Religion and Related Subjects ( ISBN 0-671-20323-1 ) .