Truth persuades by teaching, but does not teach by persuading.
Veritas autem docendo persuadet non suadendo docet.
Original text (Latin)
Notes from Wikiquote
Adversus Valentinianos (Against the Valentinians), 1.4
Original text (Latin)
Quote text and notes from Wikiquote: Tertullian (page history), available under CC BY-SA 4.0. Source quality and labels are our own summary of what Wikiquote records.