Neither dirt, sand, nor rocks, nor other lifeless matter, can provide nourishment to maintain the continuing renewal of energy upon which living things depend. It is the mark of civilized people to reject the consumption of human life in this endeavor. Vegetarians and vegans would like to extend this exception to other animal life forms, a choice that does not negate the underlying fact that living organisms must sustain themselves at the expense of other forms of life. They have simply chosen to confine their dietary choices to "vegetable" rather than "animal" categories.