Since utility is a psychic feeling and a subjective thing, it cannot be measured in quantitativeterms. In real life, consumers are only able to compare the satisfactions derived from variousgoods or various combinations of the goods. In other words, in the real life consumer can stateonly whether a good or a combination of goods gives him more or less, or equal satisfaction ascompared to another. Thus, economists like J.R. Hicks are of the opinion that the assumption ofcardinal measurability of utility is unrealistic and therefore it should be given up.(2) Hypothesis of independent utilities is wrong:
Utility analysis also assumes that utilities derived from various goods are independent. Thismeans that the utility which a consumer derives from a good is the function of the quantity ofthat good and of that good alone. In other words, the assumption of independent utilities impliesthat the utility which a consumer obtains from a good does not depend upon the quantityconsumed of other goods; it depends upon the quantity purchased of that good alone.On this assumption, the total utility which a person gets from the whole collection of goodspurchased by him is simply the total sum of the separate utilities of various goods. In otherwords, utility functions are additive.Neo-classical economists such as Jevons, Menger, Walras and Marshall considered that utilityfunctions were additive. But in the real life this is not so. In actual life the utility or satisfactionderived from a good depends upon the availability of some other goods which may be eithersubstitutes for or complementary with each other. For example, the utility derived from a pendepends upon whether ink is available or not.On the contrary, if you have only tea, then the utility derived from it would be greater but ifalong with tea you also have the coffee, then the utility of tea to you would be comparativelyless. Whereas pen and ink are complements with each other, tea and coffee are substitutes foreach other.It is thus clear that various goods are related to each other in the sense that some arecomplements with each other and some are substitutes for each other. As a result of this, theutilities derived from various goods are interdependent, that is, they depend upon each other.Therefore, the utility obtained from a good is not the function of its quantity alone but alsodepends upon the existence or consumption of other related goods (complements or substitutes).It is thus evident that the assumption of the independence of utilities by Marshall and othersupporters of marginal utility analysis is a great defect and shortcoming of their analysis. As weshall see below, the hypothesis of independent utilities along with the assumption of constantmarginal utility of money reduces the validity of Marshallian demand theorem to the one-commodity model only.