I thought I would begin with a quote

from one of the most famous economists of all time,

the Scottish philosopher Adam Smith.

And he really is the first real economist in the way

that we view it now.

And this is from his The Wealth of Nations, published in 1776,

coincidentally the same year as the American Declaration

of Independence.

And it's one of the most famous excerpts.

"He generally, indeed," he being an economic actor,

"neither intends to promote the public interest

nor knows how much he is promoting it.

By directing that industry--" so the industry in control

of that individual actor-- "in such a manner as its produce

may be of the greatest value, he intends only his own gain."

He intends only his own gain.

"And he is in this, as in many other cases,

led by an invisible hand to promote an end which

was no part of his intention."

And this term "invisible hand" is famous.

"Led by an invisible hand to promote

an end which was no part of his intention."

He's saying, look, when individual actors just

act in their own self interest, that often, in aggregate,

leads to things that each of those individual actors

did not intend.

And then he says, "nor is it always

the worse for society that it was no part of it."

So it's not always necessarily a bad thing.

"By pursuing his own interest, he frequently

promotes that of the society more effectually then when

he really intends to promote it."

So this is a pretty strong statement.

It's really at the core of capitalism.

And that's why I point out that it was published the same year

as the American Declaration of Independence,

because obviously, America, the Founding Fathers,

they wrote the Declaration of Independence, the Constitution.

It really talks about what it means

to be a democratic country, what are the rights of its citizens.

But the United States, in the overall experience

of an American, is at least as influenced

by the work of Adam Smith, by these kind

of foundational ideas of capitalism.

And they just both happened to happen around the same time.

But this idea, it's not always that intuitive.

Individual actors, by essentially pursuing

their own self-interested ends, might be doing more for society

than if any of them actually tried

to promote the overall well being of society.

And I don't think Adam Smith would say that it's always

good for someone to act self-interested,

or that it's never good for people

to actually think about the implications of what they're

doing in an aggregate sense.

But he's saying that frequently, this self-interested action

could lead to the greater good, could lead to more innovation,

could lead to better investment, could

lead to more productivity, could lead

to more wealth, a larger pie for everyone.

And when he makes this statement,

he's actually making a mix of a microeconomic

and a macroeconomic statement.

Micro is that people, individual actors,

are acting in their own self-interest.

And the macro is that it might be good for the economy

or for the nation as a whole.

And so now, modern economists tend to divide themselves

into these two schools or into these two subjects.

Microeconomics, which is the study of individual actors.

Microeconomics.

So those actors could be firms, it could be people,

it could be households.

And you have macroeconomics, which

is the study of the economy in aggregate.

Macroeconomics.

And you get it from their words.

Micro, the prefix, refers to very small things.

Macro refers to the larger, the bigger picture.

And so microeconomics, just to restate it,

is essentially how actors make decisions.

Or I guess we could say allocations--

decisions/allocations-- of scarce resources.

And you're going to hear the word scarce resources a lot

when people talk about economics.

And a scarce resource is one that you

don't have an infinite amount of.

For example, love might not be a scarce resource.

You might have an infinite amount of love.

But a resource that would be scarce

is something like food or water or money or time or labor.

These are all scarce resources.

And so microeconomics is well, how

do people decide where to put those scarce resources?

How do they decide where to deploy them?

And how does that affect prices and markets and whatever else?

Macroeconomics is the study of what

happens in aggregate to an economy.

So aggregate, what happens in aggregate

to an economy from the millions of individual actors?

We now have millions of actors.

And it often focuses on policy-related questions.

So do you raise or lower taxes?

Or what's going to happen when you raise or lower taxes?

Do you regulate or deregulate?

How does that affect the overall productivity when you do these?

So its policy, top-down questions.

And in both macro and microeconomics,

especially in the modern sense of it,

there is an attempt to make them rigorous,

to make them mathematical.

So in either case, you can start with some

of the ideas, some of the philosophical ideas

or the logical ideas, that, say, someone like an Adam Smith

might have.

And they are basic ideas about how people think,

how people make decisions.

So philosophy of people, of decision

making in the case of microeconomics.

And then you make some assumptions about it,

or you simplify it.

So I'll write this.

You simplify it.

And you really are simplifying.

You say, oh, all people are rational.

Or all people are going to act in their own self-interest.

Or all people are going to maximize their gain.

Which isn't true.

Human beings are motivated by a whole bunch of things.

But you simplify these things so that you

can start to deal with it in kind of a mathematical way.

So you simplify it so you could start

dealing with it in a mathematical sense.

And this is valuable.

It can clarify your thinking.

It can allow you to prove things based on your assumptions.

And then you can start to visualize things mathematically

with charts and graphs and think about what will actually

happen with the markets.

So it's very, very valuable to have

this mathematical, rigorous thinking.

But at the same time, it can be a little bit dangerous,

because you're making these huge simplifications.

And sometimes the math might lead you

to some very strong conclusions, which

you might feel very strongly about, because it looks

like you've proven them the same way that you

might prove relativity.

But they were based on some assumptions

that either might be wrong, or might be oversimplifications,

or might not be relevant to the context

that you're trying to make conclusions about.

So it's very, very important to take it

all with a grain of salt.

To remember that it's all based on

some simplifying assumptions.

And macroeconomics is probably even more guilty of it.

In macroeconomics, you're taking these deeply complicated

things-- the human brain, how people act and respond

to each other-- and then you're aggregating it

over millions of people.

So it's ultra complicated.

You have millions of these infinitely complicated people

all interacting with each other.

So it's very complicated.

Many millions of interactions.

And fundamentally unpredictable interactions.

And then trying to make assumptions on those.

And then doing math with that that could lead you

to some conclusions, or might lead you to some predictions.

And once again, it's very important.

This is valuable.

It's valuable to make these mathematical models,

to make these mathematical assumptions,

these mathematical conclusions.

But it always needs to be taken with a grain of salt.

And so that you have a proper grain of salt,

and so that you're always focused on the true intuition.

And that's really the most important thing

to get from a course on economics.

So that you can truly reason through what's

likely to happen, maybe even without the mathematics.

I'll leave you with two quotes.

And these quotes are a little bit funny.

But they really, I think, are helpful

things to keep in mind as you start to especially go deep

into the mathematical side of economics.

So this right over here is a quote

by Alfred Knopf, who was a publisher in the 1900s.

"An economist is a man who states the obvious

in terms of the incomprehensible."

And I'm assuming when he's talking

about the incomprehensible, he's referring

to some of the mathy stuff that you see in economics.

And hopefully we'll make this as comprehensible as possible

and see that there is value in this.

But it's a very important statement he's making.

Oftentimes it's stating a common sense thing.

It's stating something that's obvious.

It's obvious.

And it's very important to always keep that in mind,

to always make sure that you have the intuition for what's

happening in the math, or to know

when the math is going in a direction that might be strange

based on an oversimplifications or wrong assumptions.

And then you have this quote over here

by Laurence J Peter, most famous for Peter's Principles,

professor at USC.

"An economist is an expert who will know tomorrow

why the things he predicted yesterday didn't happen today."

And once again, important to keep in the back of one's mind.

And this is especially relevant to macroeconomics,

because in macroeconomics, there's

all sorts of predictions about the state of the economy-- what

needs to be done, how long will the recession last,

what will be the economic growth next year,

what will inflation do.

And they often prove to be wrong.

In fact, few economists even tend

to agree on many of these things.

And it's very important to realize

that, because oftentimes, when you're

deep in the mathematics of the economics,

it might seem to be a science like physics.

But it's not a science like physics.

It is open to subjectivity, and a lot of that subjectivity

is all around the assumptions that you choose to make.