Neoclassical economics has two main theories, but they both have flaws. Keynes tried to fix this with his ideas on unemployment, but they didn't fully work. Menger came up with a new way to think about how prices and expectations affect the economy. Basically, prices today are based on what people think prices will be in the future. If everyone agrees on future prices, things stay stable. But if people have different ideas, it creates opportunities for trading and changes in prices. This cycle can keep going without reaching a true balance.