This very interesting debate seems to boil down to whether or not it is valid and useful to promulgate a single numerical index to try to represent and quantify the multi-dimensional nature of poverty (secondary questions relate to how best to do so if the answer is yes). Whatever the theoretical pros and cons I think the reality is that we use such "simple" indexes all the time both because we have become used to getting our information in sound-bite form and because at the end of the day there are times when you need a single metric for decision-making purposes. Witness the widespread use of GDP, which everyone agrees is grossly inadequate and misleading since it's typically regarded by most people as a measure of wealth and well-being rather than as a measure of economic activity which can reflect motion without progress (the classic cases of being in a car accident, or digging a hole and refilling it both adding to GDP). So the "simple" index is a fact of life, and it's better to at least try to have it capture non-income related aspects, however imperfectly. While it may be a ridiculous proposition to compare the weight of the life (or death) of a child with that of an extra year of schooling, it's even more ridiculous to act on the assumption that the value of each is zero.