The phrase "one who should know better" refers to a person who is expected to be wise, experienced, or knowledgeable enough not to make a certain mistake or to behave foolishly. It implies that given their knowledge, age, or experience, they ought to have made a wiser or more sensible decision. This expression often conveys disappointment or criticism because the person failed to act with the expected prudence or common sense. This idiom has several nuances:
- To be wise or sensible enough to avoid certain behaviors ("You should know better than to do that").
- To understand the truth or facts better than someone else, thus should not be misled or make naive mistakes.
- In social or professional contexts, it suggests an expectation that someone has a foundational level of judgment or expertise to behave appropriately.
- It can be used when someone ignores advice, common sense, or lessons from experience that they are presumed to have.
In summary, "one who should know better" is a way of saying that a person failed to meet the reasonable expectations of knowledge or common sense their experience or position implies they have.
