At Ace of Spades HQ, Monty gives an introduction to Say’s Law:
Jean-Baptiste Say, an 18th-century economist and follower of Adam Smith, recognized one of the most fundamental laws in all economics: the entirely common-sense observation that consumption requires production. This axiom is called Say’s Law of Markets.
However, this axiom is often mis-stated as “production creates its own demand”. This is incorrect — production is necessary for consumption to take place, but production anticipates demand, it does not cause it. Production is speculative in this sense. The simple act of producing some good or service does not, in and of itself, create demand for that good or service. (This is true even for basic commodities.)
What Say’s Law really says is that production is the source of wealth. Market-driven production creates value and provides choice to consumers. Inventors and innovators bring new products to market, and as consumers are exposed to these new products, demand rises with the utility or desirability of these new products. New markets are opened by innovators who are able to tap into needs and wants that consumers didn’t even know they had until a new product or service is offered.
And he explains why money is not wealth:
So what is “wealth”, really? (I could write a whole book on the difference between “wealth” and “money”, but I’ll try to boil it down.) Wealth is options. Wealth is choice. Wealth is variety. Wealth is agency — being able to do what you want to do when you want to do it. Wealth is surfeit — having more than the essentials of life. It is comfort, leisure, ease — or at least the agency and option (those words again) to avail oneself of leisure. Simply put, wealth is stored value that can be drawn down in various ways, only some of which involve the exchange of money for goods and services. And how is wealth created? Through production, because production must necessarily precede consumption.
Money correlates with wealth because money is a medium of exchange and a store of value. Rich people have a lot of money because they are wealthy, not the other way around. Wealth allows us to buy a bigger house or better car or nicer furniture. It pays for a nice dinner for two at an upscale restaurant. Note well: wealth buys these things, not money per se. Consumption is the draw-down of wealth, not the simple expenditure of money.
Money is the oil in the machine of an economy, but money is not in and of itself wealth. If I am stranded on a desert island with a thousand gold coins, I am just as poor as if I were a homeless vagrant living in an alleyway somewhere, because I cannot exchange my gold for things I want or need. It does not give me options or variety or comfort. My gold facilitates neither production nor consumption absent a market mechanism that makes use of it.