According to Professor Mehta, many units are included in a society. The science of economics is related to the behaviour of these units. In the opinion of Mehta, in technical language, economics contains the rules of consumption and production. If an economist has full knowledge of the behaviour of the person and has complete knowledge about the environment, then he can surely tell how much he will do, how much quantity he will produce, how much quantity he will sell, how much quantity he will buy, how much quantity he will save, how much quantity he will consume, etc.

The study of the behaviour of a unit presented under the above description is micro economics. It is called micro-economics because its single unit is very small as compared to keeping together all the work together. It gives us information about the situation in which the unit is in a state of equilibrium. The study of all units simultaneously is not individual economics but macro-economics. According to Professor Mehta, the person lives in society. So, economics cannot ignore the study of macro economics, it should study not just one but all of the people.