This quote implies that common sense, or the ability to make sound and practical judgments on everyday matters, is a universally necessary trait. However, it also suggests that it is not as common as the term might imply, with few people truly possessing it. The last part of the quote emphasizes the irony that those who lack common sense are often blissfully unaware of their deficiency.

Common sense can be seen as a form of practical intelligence, separate from academic or theoretical intelligence. It involves understanding and responding to the world in a direct, straightforward manner. However, because it is so straightforward, many people may overestimate their possession of it, assuming that because they can handle complex intellectual tasks, they must also have an abundance of common sense. This can lead to overconfidence and mistakes in judgment.

In the context of today’s world, this quote is particularly relevant. With the advent of the internet and social media, we are bombarded with information and differing perspectives. Common sense is necessary to sift through this barrage and make sensible decisions. However, the same overconfidence highlighted in the quote can lead people to believe false information, make poor decisions, or fail to consider the perspectives of others.

In terms of personal development, recognizing the importance of common sense and acknowledging our potential lack of it is a crucial step. By doing so, we can focus on developing this trait, becoming more self-aware, and making better decisions. This might involve seeking diverse perspectives, questioning our assumptions, and taking time to think through our decisions rather than rushing or relying on intellectual autopilot. In this way, we can cultivate common sense and use it to navigate the complexities of modern life.