Last night, I spent a half hour with Nathan showing him how the ambient light from the street was enough for him to make out clear details. I showed him how a flashlight could be used if something frightened him or he needed to traverse the dark into the bathroom. We made a deal that during this transition time, I wouldn't keep extra lights on at his bedtime but would turn on the bathroom light before I went to bed.
I talked to him about how we can use our other senses when it's dark, like listening to the wind outside or the noises in the house. I talked about how our brains need dark to sleep and we need sleep to grow and have fun.
Nathan was relatively enthusiastic but that's not an indicative sign. He has a bad habit of trying to tell people what they want to hear rather than how he actually feels about something. (On the one hand, not great to suppress how he feels, on the other hand, some of my lessons about socially appropriate responses must be sticking.)
We'll keep trying. Or rather, I'll keep trying. Hopefully we can wean him off nightlights in such a way that he doesn't recognize how dramatic a change it is. I don't want him sitting alone and afraid in the dark. I want him to realize that he has the power to change what bothers him and that he's not helpless in the face of his fear.