What is a slippery slope argument?
This is an informal fallacy which occurs when an initial, seemingly minor, action will inevitably trigger a chain reaction, leading to increasingly severe, undesirable outcomes, often without sufficient evidence for each step.
Consider the following:
If you fail today’s easy test, you will fail the final exam.
If you fail the final exam, you won’t go to university.
If you don’t go to university, you won’t study genetic engineering.
If you don’t study genetic engineering, a cure for cancer will not be found.
If a cure for cancer is not found, millions of people will continue to die each year.
The idea is that a small, seemingly insignificant action or concession is likely to lead to far more serious, harmful, or extreme consequences. It reminds us of the English idiom ‘The thin end of the wedge’.
The slippery slope argument is considered a fallacy when the connection between the steps in the sequence is not supported by sufficient evidence or logical necessity. Note that the slippery slope fallacy is informal; that is, it is to do with the contents, not the structure of the argument.
We often encounter slippery slope arguments in practical ethics contexts, such as in the euthanasia debate. Euthanasia is the intentional act of ending a person's life to relieve incurable pain and suffering, for example when a person has a terminal illness such as cancer. Consider the following:
If you permit voluntary euthanasia in in extremis medical cases, such as for someone in terrible pain from a terminal illness with a short time to live, then you will permit voluntary euthanasia for less extreme medical cases such as chronic but non-terminal cases such as diabetes or kidney disease.
If you permit voluntary euthanasia for chronic but non-terminal cases, then you will permit involuntary euthanasia against elderly dementia patients.
Not all slippery slope arguments are fallacious: the evidence may reasonably support each step. Consider the following:
If I fail today’s easy test, then my parents will send me for tuition.
If I go to tuition, then my grades will probably improve.
If my grades improve, I will be more likely to gain admission to university.
This seems a plausible argument.
