Much of the existing literature refers to the issue of ‘weighting’, but this is only one particular form of the more general ‘aggregating’, since aggregation may take a different functional form than simply adding up. For example, if you have no food, your other capabilities will be worth very little. Some capabilities may thus be complementary capabilities, implying that their value to a person depends on the presence (or absence) of other capabilities. (Note the similarity with the notion of ‘complementary goods’ in consumer theory in economics, where it is argued that the utility of some goods is dependent on the quantity of some other goods, as in the case of pencils and erasers, or shoe polish and shoes of the same color).