What two interconnected concepts does Carson McCullers develop in this excerpt from "Loneliness . . . an American Malady"?

Love is affirmation; it motivates the yes responses and the sense of wider communication. Love casts out fear, and in the security of this togetherness we find contentment, courage. We no longer fear the age-old haunting questions: "Who am I?" Why am I?" "Where am I going?" —and having cast out fear, we can be honest and charitable.

For fear is a primary source of evil. And when the question "Who am I?" recurs and is unanswered, then fear and frustration project a negative attitude.

I chose these two concepts because in these lines the author relate love and fear comparing them one with positiveness and communication, and the other with negativity and loneliness. One (love) is the engine that keeps life going and developing happily, and the other (fear) is what keeps you from living your life happily. Love is the representation of the good, and fear the representation of the bad. They are related, the author says, because "love casts out fear". When we feel love in our lives, we automatically feel close to others and find contentment and courage. When we feel love, we feel powerful and capable of doing anything. Those are the two concepts that the author develops in the excerpt and how these two concepts are related with each other.