Wealth	Welfare	Scarcity	Growth
Adam Smith classical era.	Alfred Marshall-  neo classical era.	Lionel Robbins new age.	Paul Samuelson modern age.
An Inquiry into nature and causes of Wealth of Nations (1776).	Principles of Economics - (1890)	An Essay on the nature and Significance of Economic Science (1932).	Economics studies how men and society choose with or without the use of money, to employ scarce productive resources which could have alternative uses, to produce various commodities over time and distribute them for consumption now and in the future among various people and groups of society.
Economics is the science of wealth.	Economics is a study of mankind in the ordinary business of life, it examines that part of individual and social action which is most closely connected with the attainment and with the use of material requisites of well being. It studies wealth and man.	Economics is a science which studies human behaviour as a relationship between ends and scarce means which have alternative uses.	Economics deals with how the society uses the limited resources for alternative uses.
Deals with only the goods which are scarce and have money value	wealth and welfare of man is important.	Human behaviour  regarding choice is important.	It covers production, distribution and consumption.
Deals with consumption, production, exchange, distribution of wealth.	Only material welfare is considered, differentiates between material and immaterial things.	Economic problem arises  because of scarcity of resources.	Economics is a social science.
	By introducing welfare,  economics  becomes inexact.	Ethical aspects are not  considered so Economics is exact
	Welfare definition makes Economics classificatory.	Economics is a positive science.
		Economics is a science of individual behaviour.
		Both material and immaterial activities are considered.

Steps of Deductive method:
(i) Have a clear idea of the problem to be inquired.
(ii) Define the technical terms used. Assumptions should be precise.
(iii) Deduce hypotheses from the assumptions.
(iv) Verify hypotheses through direct observation of events and statistical methods.
Steps of Inductive method:
(i) The collected data must be systematically arranged
(ii) Based on the data, conclusions are drawn
(iii) Generalization of the hypothesis.
(iv) Verification of the hypothesis.

Nature of Economics:
(i) Nature of a subject refers to its contents, how and why they find a place in the subject.
(ii) The nature is understood by studying the various definitions given by economists.
Wealth definition:
(i) Adam Smith in his book "An inquiry into nature and causes of wealth of nations" defines Economics as a science of wealth.
Welfare definition:
(i) Alfred Marshall in his book "Principles of Economics", defines Economics as a study of mankind in the ordinary business of life;
(ii) It examines that part of individual and social action which is most closely connected with the attainment and with the use of the material requisites of well being.
(iii) It is a study of man and wealth.
Scarcity definition:
(i) Lionel Robbins in his book "An Essay on the nature and significance of economic science" defines Economics as a science which studies human behaviour as a relationship between ends and scarce means which have alternative uses.
Growth definition:
(i) Paul Samuelson defines economics as the study of how men and society choose, with or without the use of money, to employ scarce productive resources which could have alternative uses, to produce various commodities over time and distribute them for consumption now and in the future among various people and groups of society.

(ii) Since there are many definitions Keynes observed that "Political Economy has strangled itself with definitions."
Scope of Economics:
(i) It refers to the subject matter of Economics, whether it is an art or a science.
Subject matter:
(i) Economics studies the ways in which people use the available scarce resources to satisfy their unlimited wants.
(ii) It deals with consumption, production of goods and distribution of income to the factors of production.
(iii) All human activities related to wealth is the subject matter of Economics.
Arts:
(i) Since Economics provides guidance to the solution to all the economic problems it is an Art.
Science:
(i) Economics is a science since it has similar characteristics of a science.
(ii) Economics examines the causes and effects of problems. So it is considered both an art and a science.
Positive Science:
(i) Economics is a positive science since it deals with what it is, it analyses a problem on the basis of facts and examines its causes.
Normative Science:
(i) Economics is normative science because it responds to what ought to be;

The Problem of Choice:
(i) The problem of choice arises because of limited resources and unlimited wants, may relate to the allocation of resources between the goods for higher income group and the lower income group and the goods for defense and the civilians.
(ii) Since PPC is the locus of the combination of the goods the problem of choice will not arises when we choose any point on PPC.
The notion of scarcity:
(i) Every economy has scarce resources which can produce only limited amount of output even with the help of best technology.
(ii) PPC reflects the constraints imposed by the element of economic scarcity.
The solution of central problems:
(i) The solution of problem of what to produce involves the decision regarding the choice of location on the PPC.
(ii) Any point inside PPC indicates that the economy is using inefficient methods of production and inefficient combination of resources.
Conclusion:
(i) Thus the basic problems of the economy are solved with the help of PPC.

Nature of Economic Laws:
(i) A Law expresses a causal relation between two or more than two phenomena.
(ii) Marshall states that the Economic laws are statement of tendencies, and those social laws, which relate to those branches of conduct in which the strength of the motives chiefly concerned can be measured by money price.
(iii) In natural sciences, a definite result is expected to follow from a particular cause.
(iv) In Economic science, the laws function with cause and effect. The consequences predicted by the data, necessarily and invariably follow.
(v) However, Economic laws are not as precise and certain as the laws in the physical sciences.
(vi) Marshall holds the opinion that there are no laws of economics which can be compared for precision with the law of gravitation.
(vii) A physical scientist carrying out controlled experiments in his laboratory can test the scientific laws very easily by changing the conditions obtaining there.
(viii) Changes in Economic science cannot be brought about easily. As a result, prediction regarding human behaviour is likely to go wrong. There are exceptions to the Law of Demand. Thus, economic laws are not inviolable.
(ix) As unpredictability is invariably associated with the economic laws. Marshall compares them to the laws of tides. Just as it cannot be predicted and said with certainty that a high tide would follow a low tide, unpredictability prevails in Economics. Human behaviour is volatile.
(x) Economic laws are not assertive but they are indicative. The Law of Demand, for example, states that other things remaining the same, the quantity demanded of a commodity increase, as its price decreases and vice versa.
(xi) The use of the assumption 'other things remaining the same' (ceteris paribus) in Economics makes the Economic laws hypothetical. It might be argued that the laws in other sciences can also be called hypothetical. It should be admitted however that in the case of Economics, the hypothetical elements in its laws are a little less pronounced than in the laws of physical sciences.
(xii) But since money is used as the measuring rod, laws in economics are more exact, precise and accurate than the other social sciences. As the value of the measuring- rod money is not constant, there is always a hypothetical element surrounding the laws of. Economics.
(xiii) Some economic laws are simply truisms. For example, saving is a function of income. Another example of truism is human wants are unlimited.