What do Keynesians mean when they say that the economy is inherently unstable? “What matters is not whether the economy is self-regulating, but whether prices and wages are flexible and adjust...

What do Keynesians mean when they say that the economy is inherently unstable? “What matters is not whether the economy is self-regulating, but whether prices and wages are flexible and adjust quickly.” Comment. According to Keynes, why might aggregate demand be too low?