大錯誤往往從小錯誤開始。人說一句謊話，可能需要用十句謊話來圓。于是，“滑坡效應”開始了。

Slippery slope is a process or series of events that is hard to stop or control once it has begun and that usually leads to worse or more difficult things.
“滑坡效應”指的是一旦開始便難以阻止或駕馭的一系列事件或過程，通常會導致更糟糕、更困難的結果。

Telling little fibs leads down a slippery slope to bigger lies — and our brains adapt to escalating dishonesty, which makes deceit easier, a new study shows. |
根據一項最新研究，撒個小謊往往會導致“滑坡效應”，從而說下更大的謊言。我們的大腦也會適應這種謊越撒越大的情況，使得撒謊變得更容易。

“滑坡效應”也被稱為“滑坡謬誤”，這在生活中很常見。

If you break your diet and have one cookie tonight, you will just want to eat 10 cookies tomorrow, and before you know it, you will have gained back the 15 pounds you lost.
比如如果你今晚破壞節食計劃，吃一塊餅干，你明天就會想吃十塊，還沒等你反應過來，你就會把減掉的那15磅肉長回來。

所以明智的選擇是，從一開始就不要踏上斜坡。

***on a slippery slope***

如果用on a slippery slope 來形容某人或某事所處的狀態，意思就是情況越來越糟，急劇下滑，如果不及時采取措施就會變得更糟 (有時也可以說 going downhill 滑坡) 。

例如

With his big drinking problem he was on a slippery slope to bad health.
他酗酒很嚴重，健康狀況越來越糟。

如果某人被形容為 as slippery as an eel 意思就是此人奸詐狡猾，說明此人是靠不住的、不誠實的，而且很難捉住這個人的破綻。

例如

I wouldn't recommend doing business with Bob; he's as slippery as an eel.
我不推薦和鮑勃做生意，他很狡詐。

（中國日報網英語點津 yaning）