Everyone’s Poop: Texas Monthly December 2007: "They say that shit runs downhill. This is commonly understood to mean that the world is an unfair place, except among those few people who actually work with the substance, for whom it is considered something of an article of faith." via [ The Informed Reader ]
And it is an article of faith, as I can personally testify to from my time working at a waste water treatment plant. Ask the people who work there what the most important invention and they'll say the toilet.