* Subjective Theory of Value: This theory emphasizes that the value of a good is not inherent in the good itself, but rather determined by the individual's subjective estimation of its usefulness.
* Marginal Utility: Menger explained that the value of an additional unit of a good decreases as one consumes more of it. This concept is crucial in understanding consumer behavior and the determination of prices.
* The Theory of Imputation: This theory explains how the value of higher-order goods (e.g., a machine) is derived from the value of the lower-order goods (e.g., raw materials) that are used to produce them.
* The Concept of "Originary" Factors of Production: Menger identified land, labor, and capital as the fundamental factors of production, arguing that they are not derived from other factors.
In addition to "Principles of Economics", Carl Menger also wrote several other significant works:
* "Investigations into the Method of the Social Sciences" (German: _Untersuchungen über die Methode der Sozialwissenschaften und der politischen Ökonomie insbesondere_) (1883), which delved into the methodological foundations of economics.
* "The Errors of Historicism in German Economics" (German: _Die Irrthümer des Historismus in der deutschen Nationalökonomie_) (1884), a critique of the historical school of economics.
* "On the Origin of Money" (German: _Über den Ursprung des Geldes_) (1892), which explored the evolutionary emergence of money as a medium of exchange.
Menger's work had a profound impact on the development of economic thought, particularly in the Austrian School. His contributions helped to establish the foundations of microeconomics and continue to be relevant for understanding economic phenomena today.