In light of a recent dust-storm of controversy on the Internet about a certain pastor publishing on controversial (and secondary) matters, I re-offer these reflections...
"Polemics" simply means the art of dispute, or how to argue with others. Let me first recommend to you the late Roger Nicole's brilliant article, "Dealing With Differences." Read that, and deeply internalize it.
But I want to add some of my own thoughts about polemical theology, particularly how to avoid a serious argumentative fallacy. I'll call this some ABC's of Arguing With Others.
Let's say, for example, that you are in a disagreement with somebody who holds Views A, B, and C. Let's say that as you think about A, B, and C you work out logically in your mind that if somebody is consistent with A, B, and C, somehow, some way, somewhere down the road they are going to end up at Views X, Y, and Z. Now, you were already uncomfortable with A, B, and C. A, B, and C, to your mind, are questionable views. But X, Y, and Z... well, now, they are views that are completely unacceptable! A, B, and C are some things that maybe we could perhaps agree to disagree about. But let's say that X, Y, and Z are views that, say, are complete heresy and impossible for a Christian to hold. And, in the course of your disagreement, you have figured out that A, B, and C logically lead to X, Y, and Z.
Here's the principle you should remember: just because you have worked out that ABC logically leads to XYZ, does not mean the person you're arguing with has worked it out that way.
You cannot effectively argue with somebody by saying, "You believe in ABC? Well, then, you believe X, Y, and Z, too!" You see, they may not agree with you that A, B, and C leads to X, Y, and Z. They might see how it could possibly lead to X, Y, and Z, but they might also believe other things that keep them from getting there. If you want to argue fairly, if you want to argue in a God-honoring way, you will believe the best about your opponent. You will give them a charitable judgment, and not simply assume that because you've figured out that A, B, and C lead to heresy that your opponent is, therefore, a heretic.
We are all on a journey. You might have "got there" in your logical mind, but he might not have "got there" at all. You would be doing a grave injustice to tell this Jesus-loving, well-intentioned (but perhaps misguided) Christian that he's a heretic. All of this is to say that the principle I've articulated here, the ABCs of Arguing With Others, is nothing less than the second great commandment: Love your neighbor as yourself. Or, as Jesus put it so memorably, "Do unto others as you would have them to do you." In other words: interpret others the way you yourself would want to be interpreted. You do not want people jumping to conclusions and attributing to you things you don't believe. So don't do that to others. Interpret people in the best light possible, not the worst light possible.
The truth is that we all have certain roots in our theological outlook that, if taken all the way out to the extreme end of the logical road, would lead us into some heresy or another. We are often blinded by our own sin, by our own ignorance, by our pride, or by our natural limitations. We "see through a glass darkly," as Paul put it.
But here's some good news: By God's grace, we very often are not consistent at all with our bad theologies. By the grace of God, we don't get from our bad ABCs to the heretical XYZs. Spurgeon once said that "Every Arminian is a Calvinist when he prays." A clever phrase, yes. But also deeply, deeply profound. A consistent Arminian who believes that God is impotent to change people would not pray for others. And, yet, in God's grace, a vast multitude of Arminians nevertheless get on their knees and pray for their friends, their co-workers, or their family members. God often helps us to be happily inconsistent.
Recognizing this fact will help us to keep the Golden Rule when arguing with others, to believe the best about them, and not leap right off the bat from the ABCs to the XYZs. This doesn't mean we can't try to persuade our friends that their ABCs lead to XYZs. But it does mean that we will initially treat them as if they haven't already got there. And, as a practical benefit, if you keep this Golden Rule or the ABCs of Arguing With Others, you're far more likely to persuade them! Keeping this in mind will produce fruitful and edifying debate, not, as is far too often the case in theological debate, self-righteousness and dissension.