Smith was an economist who led a new school of classical economics.
Classical political economy is a school of thought that prospered, originally in Britain, in the late 18th and early-to-mid 19th century. Adam Smith is one of its main thinkers.
The concept of laissez-faire refers to Little government intervention in the economy.
Laissez-faire is an economic theory from the 18th century that resisted any government interference in business operations.
The theory that governments should assist in economic crises through fiscal and monetary policy can be credited to Keynes
Keynesian economy states that, since aggregate demand is unpredictable and unstable, a market economy will frequently end in an economic recession and inflation. And the only way to mitigate those is with monetary policy actions by the central bank and fiscal policy actions by the government.