This confusion has been stalking my mind since my growing understanding, although very minimally, of the language and idioms I’ve learned. I’ve always taken it as a general rule that we apply it to situations where people should have “known better.” What gets me is that it’s a sweeping generalization that we all share in this common knowledge. When I hear the words common and sense in the same sentence, my reaction, although said aloud in my head, is “not all sense is common.” It’s like being expected to know that which you don’t. My point, however, is what makes sense or sensibility common, as majority should know, and who determines it? I, from the standpoint of young student and with little life experience, am confused by what I should already know to be “common sense.” When I’m told that I should have used my “common sense” I feel somewhat puzzled. I’m posting this as a general inquiry on the subject. For those who wish to share their thoughts or would like to constructively correct me on the topic, I greatly encourage replies.