There are a number of terms whose meanings have not changed over the centuries, nor are they likely to. From this we may deduce that manual labour is a form of capital. All three types are required for a properly balanced economy. There exists no relationship between inflation and a depression or a recession. Populations Fairly obviously, people are quite important to the arcane science of economics.
Directions Consider something widely used, and absolutely essential.
There is no nation on earth which does not have some clothing or bedding industry, typically with manufactories in competition. For the moment, just ignore the fact that cloth wears out. Consequently, the established brands must take some competitive action. Quite reasonably, we may postulate that any manufactory must charge a certain minimum price for its goods, simply to make a profit. This profit is absolutely essential to provide a buffer of wealth for replacement of old machinery, factory expansion in good times or rebuilding after bad times.