Everyone has different perceptions of the same reality. Everything that we experience is altered by our individual perceptions. There is one reality, but each person experiences slightly different versions of that reality. The source or reason for this is the individual experiences of each person. Everything we experience in our lives piles up to form our past. Our memory brings back experiences from this heap of the past. These memories combine with the reality we are experiencing in the present to form our individual perception of reality.
Everything is perceived differently by each person, and different perceptions of reality vary greatly. An potato is a completely different thing to a farmer and a chef. The idea of music is completely different to a musician and a deaf person. Hitler was a completely different person to a Nazi and a Jew. Even though there is really only one real idea of a potato, one definition of music, and one Hitler, many different realities of these exist within people's perception.
History is convoluted by perception. There are two ways of looking at history: through our own memories and perception, and through that of others. It is impossible to preserve history in its ideal form. If we look at history through our own memories, we will not see the reality of