A Law expresses a causal relation between
two or more than two phenomena.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.In natural sciences, a definite result is expected to follow from a particular cause. In Economic science, the laws function with cause and effect. The
consequences predicted by the data,necessarily and invariably follow.However, Economic laws are not as precise and certain as the laws in the physical sciences. Marshall holds the
opinion that there are no laws of economics
which can be compared for precision with the law of gravitation.
A physical scientist carrying out
controlled experiments in his laboratory can
test the scientific laws very easily by changing
the conditions obtaining there. Changes in
Economics 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.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. 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 increases, as its
price decreases and vice versa.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.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 an hypothetical element surrounding the laws of Economics.Some economic laws are simply
truisms. For example, saving is a function
of income. Another example of truism is:
human wants are unlimited.