"The delict of heresy in its commission, penalization, absolution" : the full title given by Father MacKenzie (later Bishop MacKenzie) to his 1932 theological and canonical study gives the clearest possible picture of its contents. This is a work of serious scholarship - originally written as a doctoral dissertation. Layfolk or clergy, ordinary readers or specialists will all find in its pages a mine of thoroughly documented information about what heresy is, how it is committed, what punishments are incurred by heretics and how the repentant heretic is absolved and reconciled.