Recently, I have found the "slippery slope" argument being used quite a bit among conservative Evangelical Christians to argue that holding certain beliefs will inevitably lead to belief in a number of bad things, usually theological liberalism. Do you believe in: women in ministry; continuation of the spiritual gifts; or, a different interpretation of any passage in the Bible that threatens the status quo? Then, as the argument goes, you may be on the "slippery slope" towards liberalism.
Yet, there are several problems in using the "slippery slope" argument. For example, today's comic by Scott Adams (June 06th, 2015) shows how Dilbert's boss uses a "slippery slope" argument as a way to stop a conversation and avoid solving a problem at work. You can access this comic here. As seen in this comic, a "slippery slope" argument does not answer questions, resolve arguments, or provide solutions to problems.
Given this, why do people invoke this argument? It can be used to shut down debate. It is a conversation stopper! In using this argument, a person conveys the message that it is more important to control the argument than to answer questions or debate important concepts.
A few other problems include:
1. The misuse of the truth is a slippery slope, itself. I have noticed that people invoking the slippery slope argument only see one slippery slope that leads to liberal doctrine and diluting the Gospel message. They do not see how their refusal to debate an issue on its own merits can be a slippery slope towards legalism and intellectual rigidity, even if they are doctrinally correct.
2. Those who invoke the "slippery slope" argument do not see how this argument can be used against them, as well. For example, I once had a Roman Catholic friend who argued that the Reformation was wrong because it put the Church on the "slippery slope" to disunity and opened the door to doctrinal heresy. Ironically, many of my friends today who invoke the "slippery slope" argument are Protestants who do not see how this argument can be used against them.
3. Invoking the "slippery slope" argument does not prove or disprove a proposition. Much like an ad hominem argument, if you cannot win with logic and facts, attack the man. That is, if you cannot win an argument, resort to the "slippery slope" to shut down debate.
Indeed, I find it hard to refute "slippery slope" arguments because it shuts down the discussion. It suggests that no matter how correct my proposition may be, it must be wrong because it inevitably leads to something worse. This is why it is so important to understand that "slippery slopes" go both ways: they not only can lead to false doctrine and a dilution of the Gospel, "Slippery slopes" can also lead to legalism and rigidity.
One way to avoid the temptation to use the "slippery slope" argument is to check one's motives. Paul wrote, "Let your speech always be gracious, seasoned with salt, so that you may know how you ought to answer each person" (Colossians 4:6 ESV). Are you trying to provide a proper answer, or are you trying to control the argument and control the other person?
Again, one can avoid the “slippery slope” argument by addressing issues each on their own merit. If something is true (for example, that salvation is by faith in Christ alone, and not by works - Ephesians 2:8-10), then we must argue for this truth and not be swayed that such beliefs may be "slippery slopes" towards Church disunity. Can you argue for a doctrine on its own merits?
Certainly, if a belief or doctrine is wrong, then one must persuade others of its error. In doing so, we must be like the Jews of Berea who “received the word with all eagerness, examining the Scriptures daily to see if these things were so” (Acts 17:11 ESV). This is necessary because, as John Locke wrote,
All the Life and Power of true Religion consists in the inward and full perswasion of the mind: and Faith is not Faith without believing…true and saving Religion consists in the inward perswasion of the Mind, without which nothing can be acceptable to God.
- A Letter Concerning Toleration, edited by James H. Tully, 1983, Hackett Publishing Company, Inc., p. 26-27.
Using the "slippery slope" argument does not effectively persuade someone about the truth of a belief or proposition. At best, this argument installs an unhealthy fear in a person rather than nurturing a living faith. At worse, it fails to refute bad doctrine or promote the message of Christ. It is an argument based on fear, and is motivated by fear. Therefore, Christians must seek to persuade others of the truth of a doctrine with the help of the Holy Spirit rather than shut the argument down with fear.