"Natural Selection" could be the physical expression of Eric's perceived superiority. "Natural Selection" - on the surface an odd phrase for Eric to find some credence in, especially considering his grave misunderstanding of the topic. But when viewing Eric's repurposing of the phrase, combining aspects of social Darwinism with Naziesque conceptualizations of eugenics, Eric's behavior during the first half of the massacre makes sense. Eric wanted to shape the world to his liking, he often mentions ethnic cleansing and annihilation of 'stupid people' in his journal. Whereas Dylan's shirt implies an unleashed energy, Eric's implies a cold scientific determinism. Eric is simply enacting his natural right, by this measure, to mow down his classmates. Why? Because they are the "retards, people with brain fuck ups, drug addicts," and, most grievously of all, the "people who can’t figure out how to use a fucking lighter." They are the vapid sheep who have plagued his life, not just by their actions against him, but just by sheer virtue of their placid ignorance. "Natural Selection" is the "natural" order of things, after all.