an ardent early supporter of a cause or reform
any important Christian missionary -- especially the first to a country or region
an apostle of revolution
A book is a mirror; if an ass peers into it, you can not expect an apostle to peer out.
and Ernest rose before me transfigured, the apostle of truth, with shining brows and the fearlessness of one of Gods own angels, battling for the truth and the right, and battling for the succor of the poor and lonely and oppressed.