Which economist is credited with giving the General Equilibrium Theory in economics?

Introduction / Context:
This question deals with basic economic theory and the history of economic thought. General Equilibrium Theory is an important concept that explains how supply and demand in many markets interact simultaneously. Knowing which economist first formulated this theory helps students link names to foundational ideas in microeconomics.

Given Data / Assumptions:

• The concept in question is General Equilibrium Theory.
• The options list J. M. Keynes, Leon Walras, David Ricardo, Adam Smith and Alfred Marshall.
• We assume standard textbook level definitions of general and partial equilibrium.

Concept / Approach:
General equilibrium studies the simultaneous interaction of many markets and agents, rather than focusing on a single market. The pioneering formal model of general equilibrium in mathematical form is associated with the French Swiss economist Leon Walras. Keynes is more associated with macroeconomics and aggregate demand; Ricardo with comparative advantage; Adam Smith with the invisible hand and classical economics; Marshall with partial equilibrium analysis. Therefore, the answer requires matching each economist with their main contributions.

Step-by-Step Solution:
Step 1: Recall that Leon Walras developed a system of equations to describe the simultaneous determination of prices in many markets. Step 2: This framework is called General Equilibrium Theory and is a cornerstone of neoclassical economics. Step 3: J. M. Keynes is best known for The General Theory of Employment, Interest and Money and for macroeconomic theories, not for the original general equilibrium model. Step 4: David Ricardo developed ideas such as comparative advantage and rent, not the general equilibrium framework. Step 5: Adam Smith and Alfred Marshall contributed to classical and partial equilibrium analysis but are not credited with the first general equilibrium theory. Step 6: Therefore, Leon Walras is the correct answer.

Verification / Alternative check:
Many microeconomics textbooks introduce partial equilibrium analysis with Marshall and then move to general equilibrium with Walras. When reading history of economic thought, Walras is consistently mentioned as the pioneer who turned economics into a mathematical system of simultaneous equations. This repeated association across multiple sources confirms that general equilibrium theory is attributed to Walras.

Why Other Options Are Wrong:
Option A (J. M. Keynes) is wrong because although he transformed macroeconomics, his work focused on aggregate demand, not on multi market equilibrium in the Walrasian sense.
Option C (David Ricardo) is incorrect because his main contributions relate to international trade and distribution, not general equilibrium modelling.
Option D (Adam Smith) is wrong; he introduced powerful ideas like the invisible hand but did not create the mathematical general equilibrium system.
Option E (Alfred Marshall) is also incorrect; Marshall developed partial equilibrium analysis in which one market is studied while assuming other markets remain unchanged.

Common Pitfalls:
Students sometimes confuse the phrase General Equilibrium with Keynes General Theory, which can lead to a wrong association with Keynes. Others may guess Adam Smith because he is a famous name. To avoid such confusion, it is helpful to remember that Walras is linked to mathematical general equilibrium, Marshall to partial equilibrium, and Keynes to macroeconomic demand management.

Final Answer:
The economist who gave the General Equilibrium Theory is Leon Walras.