Ok, so: “Allomancy, obviously, is of Preservation. The rational mind will see this. For, in the case of Allomancy, net power is gained. It is provided by an external source--Preservation's own body.”
—Harmony on Allomancy
But this seems off to me. Could Harmony have been wrong? We know that he was not all-knowing. His mind "expanded" but that only implies that he is able to logic things out better, not that he gains new knowledge, right? To me the statement "Allomancy, obviously, is of Preservation...For, in the case of Allomancy, net power is gained." seems inherently wrong. Why would a force of preventing change oversee an ability that gives power? Even the way that the statement is structured seems to imply that he is "logic-ing" it out with the information he has, which is that there are only two Shards. But what if there is or was another?