I was talking to some financial planning students recently and they asked me how they should analyze a client’s circumstances to ensure good retirement outcomes. They essentially wanted to know how they could guarantee that all would be well.

It was tough to break it to them that they were seeking the impossible. “Sorry, guys. That animal just doesn’t exist. By the time we get done with all the uncertainties, variables and possibilities of a single human’s life, the numbers on your spreadsheet are essentially just an illusion. They may look real and may be more useful than nothing, but they are still illusory.”

Financial planners work with an invariable truth: The law of large numbers does not apply to small numbers. Each client’s future is essentially unpredictable given the abundance of variables. You hope the money lasts, but the certainties yield inexorably to uncertain life spans and states of health, acts of nature, volatile business cycles, unstable dependents, unforeseeable client responsibilities, irregular business … just to name a few of the realities we all face. The world is a fickle place—and the money doesn’t care.

It would be nice if we could actually rely on our wondrous spreadsheets and graphs. Often, all the client wants is the sense of certainty and predictability implied by settled numbers. But, alas, the map is not the territory. Such certainties are not part of life or money, particularly not individual lives or modern money.

I know what you’re thinking. “Bummer! All that time spent with that ridiculous HP-12C calculator preparing for the CFP exams, and for what?”

Fair enough, but we have to admit to ourselves that financial planning is a tough, but inexact, profession, more art than science. Ultimately, it doesn’t lend itself to certainties of any sort—except the certainty that failures to plan and prepare will undoubtedly yield the worst results of all.

We get the big bucks when we put all of this in perspective for others, namely regular people who find money a bit mysterious.

Predictions amid uncertainty are for weathermen and actuaries. Truly predictable results simply can’t be delivered. Economists and insurance companies may deal accurately in the laws of large numbers, but we must recognize that those people are in the denominator business. Not us. We are in the numerator business, simply stuck doing the best we can, one client at a time.

I find it amusing to parse the numbers that pass for meaningful, i.e. “scientific,” analysis of investments and their use in planning for life events, especially retirement. Though clearly well-intentioned, these efforts basically yield answers that are some version of “Who knows? It’s the best we can do.” That’s how the would-be clairvoyants address such issues as Social Security elections, withdrawal rates, miscellaneous portfolio enhancement theories and the whole range of what I would affectionately call the “crystal ball business.” These prophets act as though they are operating particularly effective divining rods, their pronouncements fairly drenched with certainty. But let’s face it, when it comes to individuals and meaningful inquiry, a Monte Carlo analysis is just a fancy way of saying that life is unpredictable. And we only have 100% certainty after something happens. Otherwise, we are basically giving answers to the question, “How high is up?” It’s so easy to fall for the “lie of the decimal point,” believing that the numbers impart reliable truths simply because they foot.

Clearly, the number crunchers help us understand relevant issues with greater clarity than no analysis at all. But we must see things in perspective: Individuals are always different from one other and from spreadsheets. The best we can do is guess intelligently and then put those guesses to work within living, breathing, real-life frameworks, as best we can understand them.

Consider that idea, along with the fact that money itself really is different in these times. While money has been around for thousands of years (see David Graeber’s extraordinary book Debt: The First 5000 Years), its most recent role is unprecedented.

A funny thing happened after World War II—the newly sane world entered the Age of Money. Once kings and fascism had been eliminated in those post-war times, the new issue was how to organize people and institutions effectively to provide for social structures and economic frameworks. The Communist Bloc tried smoke, mirrors and blatant coercion, with decidedly mixed results. The Western democracies went mainly to money. In both instances, the lives of people changed dramatically.

Because this happened in the lifetimes of many of us, it is easy to assume it’s normal. In truth, our postwar world bears faint resemblance to the prewar era. Machines changed the nature of both agricultural production and manufacturing processes. No longer was a great amount of labor required for food production; agrarian and other prewar skills were often obsolete or redundant. Rosie’s rivets were no longer needed for war machines. Nonetheless, in America, the troops were returning home and they needed places to go.

The issue after the war was figuring out how to mobilize unused energies to do the jobs that needed to be done. After some strategic cobbling by economic leaders at a conference in Bretton Woods, N.H., the Western world turned to money as its primary tool of self-organization, social reorganization and wealth building.

The West needed a functional foundation for both value exchange and essential compassion. So the delegates at Bretton Woods crafted an operational international monetary system, then put it to work. Helping hands were extended to allies and former enemies alike. The Marshall Plan was implemented in Europe while Gen. Douglas MacArthur and his minions took on the restoration of Japan. In the United States, some 9 million veterans took advantage of the G.I. Bill to receive vocational rehabilitation, unemployment compensation, training and education.

It was a revolution of social mobility and fundamental demographics. Ask your clients about their families in the 1950s. Things changed considerably then, mostly for the better, and furthermore it was unprecedented. Energy was needed everywhere to help organize, stimulate and generate. Necessity had demanded of money what it does best—matching unmet needs with unused energies. Europe and Japan got rebuilt. Former soldiers got retrained and restarted as the Depression’s malaise and the war’s wholesale destruction were left behind.

But the world, like Humpty Dumpty, could not be put back together again, at least not the same way. Before the war, rural communities (and their values) dominated much of the country. Your financial plan was your family, farm and community. A retirement plan was in the backyard and an estate plan was generally some version of primogeniture. All that being said, money was not the sole source of wealth or wealth building or, for that matter, even particularly important to most people. Children had access to both parents during the day. Life was lived mostly within 20 miles of home. Neighbors were known.

Before the war, most people would have worked in proximity to where they slept and raised their families. They would have grown some or all of their own food and been responsible for basic maintenance and repairs on their houses.

After the war, it was different. People migrated increasingly to urban areas. Their work was done more and more at centralized locations.

They had their worldviews expanded by their travels and personal relationships with folks unlike themselves, namely those with different ethnicities and cultures. Men (yes, it was mostly men) commuted in spiffy new cars on freshly built roads and highways that connected them to planned communities with recently erected schools and gathering spots. They enjoyed various urban amenities like indoor plumbing and electricity, sometimes for first time. They mostly accessed their food at grocery stores. The women made room at home and work for the men returning from the war (setting the table for culture wars some 20 years later).

Medical insurance, nonexistent before the war, became an expected benefit of employment and later a political right. Retirement money frequently came from defined benefit plans rewarding loyalty and fidelity (at least until later).

America became increasingly prosperous in that time, but it also became ever more reliant on money to accomplish all of this. Indeed, virtually none of these changes would have been possible but for money. This remains the reality to the present day, when money has become the most powerful and pervasive secular force on the planet.

Unfortunately, we have not yet effectively studied or understood our relationships with our medium of exchange, nor with the awesome forces it generates. And, frankly, there is nobody who can provide this vital education in money and how to live with it—unless it is those of us providing financial advice.

And that means we must provide new contexts and understandings, including these historical ones. It is fine and dandy for financial professionals to have rules of thumb, mathematics, charts and graphs and thick financial plans, but let us understand their limitations. We also have to tell people how many variables are working for or against them: the effect of things like Moore’s law in expanding computer capacity, increased mobility, expanding life spans and the various terrors of modern life. In other words, we must explain the world in terms of all its unknown and unknowable permutations and possibilities, including rational understandings of money itself and how it affects our individual clients.

It is about the numerators. Is any work more important?

Richard B. Wagner, JD, CFP, is the principal of WorthLiving LLC, based in Denver. He is the 2003 recipient of the Financial Planning Association’s P. Kemp Fain Jr. Award, which recognizes a member who has made outstanding contributions to the profession.