The theory of economics does not furnish a body of settled conclusions immediately applicable to policy. It is a method rather than a doctrine, an apparatus of the mind, a technique which helps the possessor to draw correct conclusions.
John Maynard Keynes
Economic principles help describe why people do what they do to get what they want.
All social phenomena emerge from the choices that individuals make in response to expected benefits and costs to themselves.
It is but a very small part of man’s wants which the produce of his own labour can supply. He supplies the far greater part of them by exchanging that surplus part of the produce of his own labour, which is over and above his own consumption, for such parts of the produce of other men’s labour as he has occasion for. Every man thus lives by exchanging, or becomes in some measure a merchant, and society itself grows to be what is properly a commercial society.