In politics we are often warned of the slippery slope. In logic it is (usually) a fallacy that says that if something happens, then something bad will be the ultimate result. If President Trump can stack the Supreme Court his way, then the conservatives on the court will overturn Roe v. Wade (even though that is highly unlikely). Speaking of that case, when it became the established law of the land people said that if we could kill the preborn, soon they will say that we can kill those less than a week old, or even authorize the blanket killing of seniors. President Trump and others have used the slippery slope fallacy to claim that once we start pulling down statues of Confederate heroes, we will soon be pulling down statues of our founding fathers. An even older use of the slippery slope was the Luddite belief that machines would ultimately take all human jobs away from us, thus destroying the economy. On the other hand, it was not a fallacy when people said that letting Hitler walk into Poland and Austria unopposed would result in him trying to take over all of Europe. Invoking the slippery slope is not limited to politics, but can also be found in the church.
Recently I was in a discussion about the Lord’s Supper. In the churches of Christ, the tradition is for a group of men to come forward to pass the trays with the unleavened bread and the fruit of the vine after prayers, usually by one or two of the men serving; then the trays are passed along the rows of congregants. As part of the discussion, the idea came up that there might be nothing wrong with women helping pass the trays (since women pass them to the next person in the pews) as long as they aren’t the ones saying the prayers. This condition is based on 1 Corinthians 14:34 (“Let your women keep silence in the churches: for it is not permitted unto them to speak.”) and 1 Timothy 2:12 (“But I suffer not a woman to teach, nor to usurp authority over the man, but to be in silence.”) One of the elders was in the discussion and invoked the slippery slope: if women take that role, then eventually some will not object if they say the prayers, and then they will want to preach. In this case the slippery slope may not be a fallacy, as other congregations have gone down that slope. It could be a fallacious argument, though, unless it can be shown that the first cause was women passing trays for the Lord’s Supper.
The churches of Christ are famous as one of at least three groups that do not use musical instruments other than the human voice in the assembly. (Two other prominent groups are the Eastern Orthodox and certain Baptists.) This is based on history (no instruments were used in Christian assemblies for several hundred years) and scripture. “Speaking to yourselves in psalms and hymns and spiritual songs, singing and making melody in your heart to the Lord.” (Eph 5:19, specifying the human voice and will as the acceptable instrument) Some congregations that insist on being non-instrumental may have recorded music (a capella only) playing over the sound system before the formal worship begins. Others use recordings (sometimes a capella, sometimes with instrumental background) during the assembly to help teach new songs. Some object to these practices, saying that they are the head of the slippery slope to using “mechanical instruments of music” in worship. The argument in favor of the use of these recordings is that they help teach the congregation new songs. Interestingly, that just proves the slippery slope, because instruments in the Roman Catholic church were supposedly originally only used for choir practice, and then moved into the mass because it helped the choir. On the other hand, the use of recordings to teach songs is not the top of the slippery slope. Because these recordings are indeed “mechanical instruments of music,” those who use them are already down the slope; they may just not realize it.
Logically, the slippery slope may be considered a fallacy. In practice, as well, it is most often used to scare with no real basis in fact. Just as one may drive a curvy mountain road and not fall off, occasionally somebody does go over the side. The slippery slope argument may be used to scare, but every now and then it has basis in fact.