Colin Wilson, who died in 2013, was almost tagged with the concept of the outsider. His famous book of the same name, The Outsider, published in the fifties, was a tour de force of its type. Follow up books, Religion and the Rebel and Beyond the Outsider expanded and modified the discussion. Religion and the Rebel was a sympathetic survey of outsiders in history which revealed a amazing reading and ability to sketch the essence of a thinker. The outsider is the person who lives a life 'looking in' or an onlooker to the main activity of humanity. The outsider is forced by his shy inner nature to look through the keyhole of life. He is uncomfortable with the collective and group, eschews team spirit, of being arbitrarily included, or being in unison, of being of the school. The type is naturally solitary. He is slow to trust or like people. He can be warm and benevolent inside and convivial to the familiar group. In fact inside he might be a volcano of feeling. But he cannot express this. To others he is inscrutable. These personalities are probably discovered and rejected by in the pernicious 'human resource' psychological test. Wilson wrote of the connection between being deeply religious and being an outsider. Meaning I suppose that those who ruminate upon the elemental questions and choose an unfamiliar path which they need to walk alone. The great religious figures. Jesus, Buddha and Mohamed were arguably of the outsider caste. These persons in there exalted state stood apart from their acolytes. One who is followed is always alone. If a denomination is a party of believers then Jesus was not a Christian, the Buddha not a Buddhist and Mohamed not a Muslim.
I would say to people: look out for the outsider, do not crowd him, he marches to a different drum, he wants to be known, he wants to know, he has reservoirs of kindness and a richness of mind.
I understand that Colin Wilson intellectually moved away from his earlier writings on the outsider. In later life he moved into the paranormal and crime. This writing did not interest me.