A bone of contention is any issue or thought that triggers some type of difference of opinion between two parties, usually to the point that both parties experience some degree of animosity toward one another. Until the two parties are able to come to some sort of resolution to the conflict that is causing tension, that issue will remain something that creates a barrier in communication, and may even spill over into other matters that were once considered innocuous. Only after the two parties resolve the issue to their mutual satisfaction, either by eliminating the problem or at least deciding that it is all right to simply agree to disagree, will the matter cease to be a bone of contention that undermines the relationship.
The exact origin of the idiomatic expression is debated among linguists and others who are interested in idioms and various types of colloquial expressions. One popular school of thought holds that the phrase is representative of what happens when one dog attempts to take away a bone that is currently in the possession of another canine. Typically, the result is a heated exchange between the two animals that can escalate into a fight.
As a saying that helps describe differences of opinion between people, a bone of contention can be something as simple as a difference in the belief systems of two different people. While many people find it very easy to respect boundaries and feel no need to attack the beliefs of others, that is not always the case. When two people who are convinced their unique lines of thought are each the most correct and therefore superior to all others, chances are they will each vie to prove how the others thought processes are flawed. As a result, animosity can often develop as both parties spend more time pointing out the perceived faults of the other person’s point of view and less on seeking common ground. In this scenario, the bone of contention will often make it hard for the two parties to relate to one another on any level, even on issues in which they happen to agree.
A bone of contention can occur whenever there is a difference of opinion on any subject that escalates to the point of creating anger and negative feelings between two parties. Different thoughts on what type of fence to put around property may become an issue between neighbors. Political and religious stances can be the basis for disagreement that becomes heated and divisive. Parents may disagree on some aspect of child rearing, creating ill feelings within the family.
It is important to note that simply having differing opinions or thoughts does not mean those ideas must become a bone of contention. In many cases, people are able to share different ideas without anyone feeling threatened or find it necessary to correct the thoughts of another person. It is only when at least one party is convinced that the other must change their stance and agree with a different point of view that a issue or belief becomes a bone of contention.