You know those hypothetical "would you rather" scenarios people like to bandy about? Or, how about this: "If you had to lose one of your five senses, which one would it be?" Many people would probably say they'd part with the sense of smell before another. It's not a crazy answer, but according to this piece from Scientific American, the sense of smell is far more vital (and powerful) than most of us realize-it's a guiding mechanism for our interactions with people and the world. Link.
Also worth reading is this much-linked-to piece on the science behind free will and determinism.