“Blocks and neighborhoods aren’t concrete concepts that mean the same thing to everyone, unlike, say, things like ‘apple’ or ‘sky.’ Points of reference shift depending on the person that’s using that reference, so blocks/neighborhoods are more like alternate realities laid atop one another, like plastic sheets on an overhead projector. There’s even a phrase for the study of this murky concept: mental maps. They can help us understand why some neighborhoods thrive, others die, and how changes are made.”