Lesson #23: Why you breathe.

Even plants need oxygen to live.
This is because we're all on fire. When things burn, they oxidize. When we stop oxidizing, we die.
This is because the world was created by the grand and cosmic Space Pig (pictures coming soon) as he smokes his Leftie's Cigarettes. The smoke and particulate matter exhaled collects to form galaxies in the void.
This is the source of the spark of life.