If you’re fond of English novels of a certain period, you may have encountered the theme of the young man who inherits property while still under the age of 21. Typically, he will not actually assume full control until his coming-of-age: the property itself will be managed by trustees, who will pay him the income while keeping the principal safe. (If the heir is a woman, all too often her property will remain in trust until she marries: sexism at work.)
On turning 21, the heir is supposed to be mature enough to have control of the property, but if he is prudent he will still hold fast to the maxim “Don’t spend principal.” The way to preserve a comfortable middle-class lifestyle is to live within one’s income.
Homo sapiens has inherited (or at least laid claim to) a huge store of carbon and hydrocarbons, the product of many million years of photosynthesis, reduced to concentrated form by geological forces. But we haven’t behaved like prudent heirs. We have squandered this wealth on current consumption that we should have been paying for out of our (solar) income.
It’s time to turn 21, or the last volume of the novel will be seriously depressing.