'Demonstration' in the Bible

And He, when He comes, will convict the world about [the guilt of] sin [and the need for a Savior], and about righteousness, and about judgment:

And my message and my preaching were not in persuasive words of wisdom [using clever rhetoric], but [they were delivered] in demonstration of the [Holy] Spirit [operating through me] and of [His] power [stirring the minds of the listeners and persuading them],