The theory that I considered to be the most important is the free market. The economy should be run by free market but not entirely. Free market gives a more sufficient economy and makes the economy flow smoothly. Free market means no government intervention involved in the economy,therefore entrepreneurs have more freedom to choose what to produce in order to satisfy the needs of customers because there's no prohibition from the government. However, we have to accept that free market could easily crate market failure as there's no balance distribution of income in the market, even though some economists stated that economy has a way to stabilise itself. Poor people rarely have ways to earn money in the free market. Therefore, the economy need some organisations to act as the distributor of the wealth, actually , the government could do this role.
For my opinion, the economy should be divided into two parts, may be 70 percent of free market and 30 percent of government intervention in order to stabilise the economy in the market. This way the economy will be balance and no market failure created at this point.
I think Thomas Robert Malthus is the greatest economist because he assume that population is the main factor to lead to any economics problems, which is absolutely true because population is always the main factor. For example, when there're more poor people in the society and the government tends to offer them with welfare such as education, but still we have to accept that when the government offers more help for them, they are not going to find any ways to earn money because they think that they can always rely on the government, and therefore, they bring the country economy down. Although the government provides free eduction for their children, but what if those children create brain drain when they finish their study offered in the country. Hence, it means that the government gives them education as a door open to them because the government indeed hope that those kids will be the country's future, but it's not gonna work as those kids start to go outside the country and work for a place where offers them more benefit. It's such a waste! Government spends too much money on them but they don't give anything in return, well again, this bring the country's economy DOWN!