Maggie's Farm

A Slippery Slope fallacy is committed when there is no persuasive evidence or argument for things moving in the indicated direction.

That is bad writing, but blogging is hasty. Here's one example from Nizkor:

"We've got to stop them from banning pornography. Once they start banning one form of literature, they will never stop. Next thing you know, they will be burning all the books!"

or:

If we let Bush wiretap calls from Al Quaida, next thing you know he'll wiretap my calls to my secret grilfriend in Des Moines.

However, Slippery Slope arguments can be persuasive when there is reason to think that something will progress further:

"If you give that dog an inch, he'll take a mile."

When a slope is part of a political agenda, it is safe to assume that an issue may be in the process of being given a push down that slope, so it pays to be watchful. A strategery of "incrementalism" is often a clever political approach:

First we'll ban assault rifles, then handguns, then rifles, then shotguns, then, eventually, BB guns and finally squirt guns...and snowballs.

or

We'll focus on banning late-term abortions, which no-one likes, and move forward from there to making abortion a state issue again.

Like all of the logical fallacies we enjoy, Slippery Slope sometimes can be non-fallacious, which is from whence falllacies derive their power. Volokh recently posted an excellent example of the fallacy - with a good drawing.