Tuesday, September 9, 2008

LTD: the Slippery Slope Fallacy

Picking up on the discussion about fallacies, let’s talk about a very common one: the Slippery Slope fallacy.

The basic idea behind the Slippery Slope fallacy is that one event is simply a step along the way, and it will lead to another and another and so on until we inevitably arrive at something dire and drastic which no one wants.

Slippery Slopes assume that there is a fixed path in one direction for every choice, and that they first step along that path always and inevitably leads to the end of the path.

A good example from the Deaconess/women in diaconal ministry debate (which has become a good case study for understanding logic-- and logical error-- in theological discussion) is the following argument, which I’ve heard or read a number of times over the last several months:

If we allow women to be ordained as Deacons, it will only be a matter of time before we are ordaining them as Ruling Elders and eventually Pastors!

Now, this argument exhibits more than one fallacy (it also contains a “False Cause” fallacy, which we’ll cover another time), but it is a clear Slippery Slope. I’ll demonstrate why in just a moment.

How do you argue against a Slippery Slope fallacy? There are essentially two ways:
  • By counter-example: a counter-example is an argument that follows the same form or concept of an argument, but arrives at a different conclusion. A good counter-example will expose a Slippery Slope’s error.
  • By severing the link: a Slippery Slope depends on the assumed link between the “steps” down the slope; break that link, and you’ve demonstrated the error of the fallacy.
To illustrate: a counter-example might be, “Both the Associate Reformed Presbyterian Church (ARP) and the Reformed Presbyterian Church of North America (RPCNA) have ordained women as Deacons for decades, and both of these denominations are becoming more conservative in their theology in general, not less.”

Meanwhile, here is a severance of the link: “Your argument assumes that the office of Deacon and the office (or offices) of Ruling and Teaching Elder are essentially the same, and that a Deacon is merely an Elder-in-training or something of that sort. But Scripture makes it clear that one is inherently different from the other-- and that it is
not the case that a Deacon is simply a ‘Junior Elder.’ If the offices are different, then one doesn’t necessarily lead to the other.”

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