The thin end of the wedge
Meaning
A minor change or action that, if accepted, will lead to a series of undesirable and much more significant developments.
Origin
To split a sturdy log, you don't start with the widest part of a wedge. Instead, you introduce the narrow, sharp 'thin end' first. This initial, seemingly insignificant entry creates a crucial opening, making it inevitable that the entire, much larger wedge will follow, driving deeper and splitting the wood apart. This vivid, practical image from carpentry entered the English lexicon, gaining significant traction in the 19th century. It quickly became a powerful political and social metaphor, warning against any small, initial concession or change that, once accepted, would inexorably lead to much more significant, often undesirable, developments – just like how that first small crack inevitably gives way to a larger, uncontrollable split.
Examples
- Allowing employees to work from home one day a week is often seen as the thin end of the wedge, leading to everyone wanting a fully remote schedule.
- Many critics argued that the new zoning proposal was the thin end of the wedge, fearing it would eventually lead to uncontrolled urban sprawl.