[3] While the main focus of their work is to explain economic depressions in Europe and the reasons why they occur,[3] Malthus uses his scholarship to explore price determination and the value of goods.

[4] In Principles of Political Economy, Malthus' rebuts David Ricardo's work, particularly rejecting idea developed by Jean Baptiste Say that theorizes that supply generates its own demand, known as Say's law.

[1] After the first version's publication, Adam Smith develops the idea that an object's inherent value is related to the labor that went into its creation.

[1] Although this new conclusion would only call for revision of the sixth and seventh sections of his second chapter, Malthus uses this new revelation as an excuse to re-examine his whole book.

Twentieth century British economist John Maynard Keynes is considered an admirer of Malthus' work.

[4] Keynes cites this chapter of Malthus' book as "a masterly exposition of the conditions which determine the optimum of saving in the actual economic system in which we live.

He faults Malthus' work for being "unable to explain clearly (apart from an appeal to the facts of common observation) how and why effective demand could be deficient or excessive.

"[8] John Stuart Mill, a nineteenth-century British economist, also criticizes Malthus' Principles of Political Economy.

[citation needed] After this, economists such as John Maynard Keynes begin to look more deeply into Malthus' ideas and utilize them in their own work.