Carl Menger was an Austrian economist born in 1840, known for founding the Austrian School of Economics. He introduced the concept of marginal utility, which explains how the value of goods is determined by their usefulness to individuals rather than by the labor required to produce them. His work laid the foundation for modern economic theory and influenced many economists. Menger's most notable publication, "Principles of Economics," was released in 1871. In this book, he argued that economic phenomena arise from individual actions and choices. His ideas challenged classical economics and contributed to the development of microeconomics and subjective value theory.