Logic warns the wary of many fallacies. Everyone should master this canon of error—or you will be mastered by it. A logical fallacy is a typical way in which arguments go wrong through sloppy reasoning. Let me cite a few examples before turning to issue at hand—the slippery slope from same-sex marriage to significant changes in sexual ethics.
False dichotomy is a common and cunning fallacy. An either/or condition is set up. One must affirm either A or B, not both A and B, and not neither A nor B. A proper dichotomy works like this:
You are either with Christ or against him. This covers all the available options. The condition is exclusive: Christ or not Christ (Matthew 12:30; John 14:1-6).
Here, though, is a false dichotomy:
We should not defend the gospel; we must preach the Gospel.
This is a false dichotomy because the Bible calls us to both defend gospel and to preach the gospel (Matthew 28:18-20; 1 Peter 3:15-16).
Another popular fallacy is argumentum ad hominem, or argument against the man. Instead of critiquing someone’s argument for traditional marriage, an opponent instead attacks the traditionalist’s character and motives. Some claim that denying same-sex marriage means one hates homosexuals and lesbians. This response gives us two fallacies for the price of one.
1. The person’s character is attacked, rather than the force of his argument. This is a glaring case of argumentum ad hominem. Even if the critic hates homosexuals and lesbians (and no one should), that does not, of necessity, undermine his argument, since his argument may work independently of his motives.
2. The false dichotomy is claiming that you either (A) support same-sex marriage or (B) hate same-sex couples.
I have introduced two classic and chronic fallacies. May we avoid them! Another fallacy feeds on itself. Meet the false charge of fallacy. Those pumped up by the power of logic may hyperventilate at the prospect of proving someone wrong through uncovering a lethal fallacy. Sometimes the difference between a fallacy and a valid form of reasoning is subtle. Consider the slippery slope.
As a fallacy, the slippery slope errs by wrongly stipulating the implications of ideas: if A, then B, then C. We always slip down the slope into the abyss. “If you do this, then that will happen, and, God help us, the other thing will happen, which is horrible!” So, the slippery slope also contains a reductio ad absurdum argument. Let me illustrate.
Some complementarians claim that if churches allow women to be senior pastors, they open the door to accepting homosexuality. Since most evangelicals—at least 20 years ago, when my wife was writing much on this topic—do not accept homosexuality, then they should reject women as senior pastors as well. But for evangelicals with a high view of biblical authority and a respect for classical methods of biblical interpretation, there is no danger of any slope to slide down, since it is obvious that while the Bible records many women leaders favorably, it never endorses any homosexual activity.
