"The person we usually call introverts seem never to have learned adequately how to communicate their thoughts to others." They tend to withdraw into themselves, "They think too much." It is sometimes presumed and "such men are dangerous" Or they are shy, inarticulate and it is thought lonely. - Writing as self revaluation
this passage talks about how introvert people are sometimes withdrawn into their own world, they keep to themselves. They do not communicate with the rest of the world their thoughts and feelings, they over think and this makes them a threat no one knows what they are thinking or what they will do.
