When someone says in public that "they know everything," it could be interpreted in different ways depending on the context, the tone of the statement, and the individual's personality.
Common Expression: In some cases, saying "I know everything" could be a figure of speech or an exaggeration used casually or humorously. People often use hyperbole to emphasize their knowledge or expertise on a particular subject without necessarily believing they genuinely know everything.
Confidence or Bravado: Some individuals might use such statements to display confidence or assertiveness. It can be a way of expressing self-assurance, even if they don't mean it literally.
Grandiose Delusion: In other situations, stating that one knows everything could be a sign of grandiose delusion. Grandiose delusions are a symptom of certain psychological conditions, such as narcissistic personality disorder or some forms of bipolar disorder, where a person has an inflated sense of self-importance and believes they possess exceptional abilities or knowledge.
Determining whether it is a form of grandiose delusion or a common expression among people these days would require a more in-depth understanding of the individual, their behavior, and any other related patterns or symptoms they may display. In isolation, making a sweeping judgment about someone's mental state based solely on this statement might not be accurate.
If you encounter such behavior in someone and it seems concerning or persistent, it might be helpful to observe their overall behavior and seek professional advice if you suspect there might be underlying mental health issues. A qualified mental health professional can conduct a comprehensive evaluation and provide appropriate guidance and support.