Slippery slope

The metaphor of a "slippery slope" conjures up images of the danger of coming too close to the edge of a cliff. One step in itself may not cause you any harm, as it merely brings you down the slope a bit. But if you take enough steps toward the brink, you will reach a point where the slippery ground makes you lose your balance and tumble down over the precipice.

In rhetoric, a "slippery slope argument" is one which suggests that an innocent-seeming small action will lead inevitably to a disasterous result.

Examples:

• If we allow this increase in administrative fees, soon tuition will double!
• If we don't stop the terrorists in Iraq, they'll invade Maine next!
• If we send in 100,000 troops, the next thing you know we'll be in a quagmire like Vietnam!