As there is no perfect human, and we are all effected by biases, perceptions, environments and many other factors, it is not possible for anyone to know absolute truth or absolute reality. Therefore, truth and reality are nothing more than personal illusions. ~ ME
I would argue that no matter how two like minded persons thought alike, if they were perfectly honest with each other, eventually they would find points of discord on any subject. Then, the more people that come together, the more points of contention that can be found.