Plato's Allegory of the Cave is a story found in The Republic about being in darkness, being in the light, and the level of comfort that keeps you in one place or the other. In the story, the characters that have known nothing but the darkness (a symbol of ignorance), when introduced to the light (a symbol of knowledge), return to the cave where their familiar darkness resides. In the light, they discover that what they have believed their whole life was untrue. Instead of feeling enlightened by the revelation, they feel fear and seek the comfort of their former ignorance.
For those who are accustomed to the light, they would rather die than feel the discomfort of being trapped in darkness. For those accustomed to the darkness, the discomfort of the unfamiliar becomes a barrier that some are unwilling to cross. You can not force anyone to choose one or the other but if you desire to influence their decision, you must understand that the barrier for both is one of comfort levels.