Natural signs are those entities whose existence is dependent on preceding conditions. Therefore, the existence of a natural sign is an indication that its preceding conditions are or were actually instantiated. For example, footprints in the snow are dependent on the animal that creates them, thus footprints are natural signs. Exactly what the footprints in the snow indicate, or are natural signs of, is potentially limitless. A man's footprint could indicate his size, approximate weight, fashion preferences, even infirmities if there are characteristics of a limp. Conversely, a representation's content is not as broad, nor as unspecified. As a result, an indication relationship could be necessary for a representation relationship, but not sufficient. Furthermore, natural signs are dependent on the actual existence of their instantiating conditions while representations bear no such dependency relationships. This is the critical feature that allows representations to misrepresent something as the case when it is indeed not.
