Steve Keen said this quote

...If you look at mainstream economics there are three things you will not find in a mainstream economic model - Banks, Debt, and Money. How anybody can think they can analyze capital while leaving out Banks, Debt, and Money is a bit to me like an ornithologist trying to work out how a bird flies whilst ignoring that the bird has wings...

~ Steve Keen

This resulted in a model of the macroeconomy as consisting of a single consumer, who lives for ever, consuming the output of the economy, which is a single good produced in a single firm, which he owns and in which he is the only employee, which pays him both profits equivalent to the marginal product of capital and a wage equivalent to the marginal product of labor, to which he decides how much labor to supply by solving a utility function that maximizes his utility over an infinite time horizon, which he rationally expects and therefore correctly predicts. The economy would always be in equilibrium except for the impact of unexpected ‘technology shocks’ that change the firm’s productive capabilities (or his consumption preferences) and thus temporarily cause the single capitalist/worker/consumer to alter his working hours. Any reduction in working hours is a voluntary act, so the representative agent is never involuntarily unemployed, he’s just taking more leisure. And there are no banks, no debt, and indeed no money in this model.You think I’m joking? I wish I was.

~ Steve Keen

Have you heard the joke about the chemist, physicist and economist who get wrecked on a desert isle, with a huge supply of canned baked beans as their only food? The chemist says that he can start a fire using the neighbouring palm trees, and calculate the temperature at which a can will explode. The physicist says that she can work out the trajectory of each of the baked beans, so that they can be collected and eaten. The economist says Hang on guys, you're doing it the hard way. Let's assume we have a can opener.

~ Steve Keen

Economics also has to become a fundamentally monetary discipline—from the consideration of how individuals make market decisions through to our understanding of macroeconomics. The myth of the money illusion (which can only be true in a world without debt) has to be immediately dispelled, while our macroeconomics have to reflect a monetary economy in which nominal magnitudes matter, precisely because they are the link between the value of current output and the financing of accumulated debt. The dangers of excessive debt and deflation simply cannot be comprehended from a neoclassical perspective.The discipline must also become fundamentally empirical, in contrast to the faux empiricism of econometrics. By this I mean basing itself on the economic and financial data first and foremost—the collection and interpretation of which has been the hallmark of contributions by econophysicists—and by respecting economic history, a topic which has been systematically expunged from economics departments around the world.

~ Steve Keen