Common knowledge is a misnomer.
I personally do not believe there is such a thing as something that everyone knows as specific knowledge. I do believe there are common actions and reactions – ways in which we understand how to naturally defend or oppress which is driven by innate understandings of our environment. But common knowledge would mean that we all think the same way which would mean that we would all have to live the same lives. The reality is that we do not.
I often tell my students that they have been lied to all their lives as being “special.” I explain to them that none of us are particularly special – however – each one of us is unique. Let me explain the difference: to be special would be to say that you have lived some way of life that would put you above everyone else. You have become the epitome of everyone who wants “success.” The problem with this idea is that success is defined by each person differently in different environmental circumstances. My success may be defined by having just enough retirement savings to live another 10 years beyond retirement. Someone else my own age, living in a deep portion of the amazon in some “uncivilized” culture may see success as making it through just another day. For that person, retirement doesn’t even exist. Thus, the person that I see who has achieved the goal of saving enough to live comfortably beyond retirement becomes “special” to me, but they mean nothing to the deep amazon Brian counterpart who is constantly making sure that they survive one more day.
But to be unique – you need nothing to accomplish that. Each one of us lives a life that no one else can live. No one else on this planet can or will ever experience life the way I have. The total sum of events in my life have happened to me only in the order, consequence, and experience that I have observed them. They have completely shaped how I interact in this world, and they have created the knowledge that I have.
Thus, in sum, the knowledge I have is unique to me only. There is nothing that I have seen that can lead to a connection with some kind of common shared knowledge as the knowledge I have belongs to only me. I can use my knowledge to make connections with other people through a shared sense of experience, but the experience itself is different from individual to individual. How we interact with others comes not through what the group understands, but what the individuals understand based on their personal experiences. Commons knowledge then is nothing – common connections, that’s a different story.