The slippery slope is one of the most commonly invoked arguments and usage of slippery slope arguments seems to be on the rise. One study found that the phrase is used in the media 7 times more frequently than it was just 20 years ago (see here).

These slippery slopes are bandied about quite routinely to sway sentiment and opinion. They are typically used to argue in opposition to something, and they work pretty well. Slippery slope arguments invoke fear, inaction, and even rejection of a proposition by suggesting that if you allow a not-so-bad thing to happen, it will lead to something-much-worse happening.

We hear examples of slippery slope arguments every day. Just a few include:

• Physician-assisted suicide will open the door to the government pulling the plug on grandma to save Medicare dollars.
• If we encourage contraception, sexual promiscuity will run rampant and immorality will destroy the fabric of our nation.
• Legalizing gay marriage will result in incest, polygamy, bestiality, and the breakdown of the American family.
• Pot smoking is the gateway to heroin addiction.
• First they came for my gun; then they came for my liberty.

Like the examples above, most slippery slope arguments have extremely dubious connections between the actual and predicted events. Many are in fact completely ridiculous. Most slippery slope arguments are guilty of gross exaggeration and are a form of arguing to the extreme and to fear. They are also a form of false conclusions or invalid extrapolations that mistakenly assume that rational lines cannot be drawn to halt any slippery slope. In short, they tend to violate a large number of basic tests of logical and factual validity.

Apart from appealing to emotion and fear, there is another big reason slippery slope arguments work so well. It is because they are often quite valid. Give them an inch and they’ll take a mile is a valid truism.

“First they came for” is granddaddy of slippery slope arguments. It is traced back to a poem by Lutheran Pastor Martin Niemoller that described the decent of Germany into Nazi atrocities. It was a cautionary message about political apathy that described an actual progression of attitudes and events. As a slippery slope argument, it was perfectly valid and substantiated. It was however a retrospective analysis, not a prediction. Nevertheless, today it gets adapted into slippery slope predictions for all sorts of unlikely and implausible outcomes.

This illustrates the fact that we can often only recognize a true slippery slope after we have slid down it. Still, being cognizant and wary of a slippery slope can help us to put on the brakes and avoid sliding too far. We should not necessarily avoid slippery slopes, but we certainly should be cautious and especially sure-footed when negotiating one.

There are criteria that we can use to evaluate the amount of legitimate concern to grant to any particular slippery slope argument. Are the causes and effects that it predicts really likely on the grounds of logic and evidence? Are there any valid precedents to support this slippery slope prediction? Is it only arguing to fear? Is it really likely that such a slippery slope would not be halted before it went too far?

Not all but many invalid slippery slope arguments are put forth by religious people to defend their practices and implement their beliefs in policy. This is understandable. When you do not have facts to argue, slippery slope arguments are very easy to fabricate and usually very effective.

However, we are all guilty of putting forth invalid slippery slope arguments at times when we think it supports our position. Unfortunately this rampant misuse of slippery slope arguments tends to discredit valid slippery slope arguments. Paradoxically it seems that they work very well most of the time but at other times are dismissed out of hand as almost a pejorative. Invalid slippery slope arguments are given far too much credibility and consequently valid ones can be too easily dismissed.

We as fact-based thinkers must be especially cognizant of the rampant misuse of slippery slope arguments and only invoke them after careful consideration. When we do, we must be ready to defend those arguments with supporting evidence or rationale even as we question the basis for the slippery slope claims of others. And most importantly, we must resist the temptation to use specious slippery slope arguments even when they serve our own interests. If we do not reject all such arguments, even when they help our own cause, then we all suffer from a diminution of effective logic and reason and rational decision-making.