The Theory of Monetary Neutrality suggests that changes in the money supply only affect nominal variables, such as prices and wages, without impacting real variables like output and employment in the long run. Essentially, while an increase in the money supply can influence short-term economic activity, over time, prices adjust, and the economy returns to its natural output level. This theory highlights the distinction between real and nominal aspects of the economy, emphasizing that money is neutral in its long-term effects.