Development of the primary concept begins with establishing the supporting elements of both characters and conflict. These elements become extensions of the original idea that permit the author to explore different aspects that would not have been possible otherwise.
Through characters the author can explore the emotions and thoughts that surround a founding idea. In every action, thought and emotion the characters can reveal a different perspective. Characters are principles and perspectives through which the author can explore. A nyctophobic character that fights through the darkness to save another can emphasize the primary concept that a person can do anything to save another more than attempting to describe the concept.
Just as characters can emphasize the emotions around a singular premise, the conflict that drives these characters can identify aspects of the idea. Through conflicts the characters can be tested and emotions elevated to identify the concept behind each character.
Every narrative is born of a founding idea that the author wishes to approach and it is every subsequent element that they explore that allows them to develop the primary concept.