A fallacy is a mistake in the logic of one’s thinking or communicating which leads to wrong conclusions. We as those who desire to be clear thinking and accurate about the properties of reality need to be familiar with fallacies as we are presented with them, in order to hone our ability to rightly appraise truth claims.
Definition: The Slippery Slope fallacy is an illegitimate use of an if-then conditional statement and occurs when in order to demonstrate the unacceptability of a proposition or idea, a series of increasingly worse, but unlikely, propositions or ideas are claimed to follow irresistibly from it. NOTE: This fallacy is related to but distinct from the logical slippery slope, a legitimate application of the slippery slope, in which the progressive steps reasonably follow from the first.
Examples: Slippery slope fallacy – One should never gamble. You will become addicted to it and spend all your family’s money on it. You’ll then have to turn to a life of crime to support the habit.
Logical slippery slope – Same-sex marriage should not be legalized. If the definition of marriage is allowed to be redefined away from one man and one woman, then the number two will soon be seen as arbitrary and will lead to polygamy.
Recognizing the fallacy: Identify the initial proposition being attacked and the final event in the slippery slope sequence. If you can show principled reason why the last does not follow from the first, it is a slippery slope fallacy. If the final step does proceed logically from the first, it is a logical slippery slope.