Tim Keller continues (& concludes) his blog series on Gospel Polemics with "Gospel Polemics, Part 4: Everybody's Rule." Here's a roundup of the first six rules. A blurb from "Everybody's Rule" concerning the evil of ad hominem arguments...
...no one has written more eloquently about this rule than John Newton, in his well-known “Letter on Controversy.” Newton says that first, before you begin to write a single word against an opponent, “and during the whole time you are preparing your answer, you may commend him by earnest prayer to the Lord's teaching and blessing.” This practice will stir up love for him and “such a disposition will have a good influence upon every page you write.” Later in the letter Newton says, “Be upon your guard against admitting anything personal into the debate. If you think you have been ill treated, you will have an opportunity of showing that you are a disciple of Jesus, who ‘when he was reviled, reviled not again; when he suffered, he threatened not.’ ” It is a great danger to aim to “gain the laugh on your side,” to make your opponent look evil and ridiculous instead of engaging their views with “the compassion due to the souls of men.”
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I would even ask seminaries to consider at least one course in “Polemical Theology” which would not simply list the errors that need to be refuted, but which would teach students how to go about theological dispute in a way that accords with Biblical wisdom and the gospel.