Exceptions include the vestigial tail in us humans (coccyx to you anatomy buffs), our vermiform appendixes (appendices to Jesuit-tutored readers), that have to be yanked out when they go bad, and former Senator Strom Thurmond.

The French call it "raison d'etre," or reason for existence, something that, in terms of their current image, is becoming increasingly difficult to identify.

Elsewhere in nature, animal, vegetable and mineral species have predestined reasons for existence, which they fulfill because they have no alternatives; when they are unable or unwilling to do so, they become victims of evolution.

A stinkweed cannot, for example, aspire to become a Giant Sequoia, and a common pebble will never be a great monument, nor can a monkey rise to a position of world leadership (okay, spare me those wise-ass arguments on that last point!)

We humans, on the other hand, are predestined to only one aspect of our earthly existence - namely, its eventual end. Within that major limitation and a number of other practical constraints, we are free to search for, and strive to fulfill, our "raison under the sun."

We are also, sadly, free to opt for some degree of purposelessness, ranging from a failure to achieve our full potential to drifting like human algae on the ocean of life.

For most of us, our early decades are pre-programmed and reprogrammed by the circumstances of our birth and periodic nudges by the fickle finger of fate, so our "raisons" are largely shaped by family, health and occupational considerations, with random incursions of both good and bad luck.

Parenthood and career, often concurrent, tend to impose on us the heaviest burden of non-elective purpose, meaning that our search for time-and-energy-consuming activities is no more challenging than getting wet in a rainstorm or picking lottery numbers that don't pay off.

Those of us not earlier harvested by the grim reaper then advance (or is it a retreat?) to geezerdom, wherein inescapable scourges, such as maltuition (not a misprint), plasticarditis and PTA parties are gradually left behind and replaced with free time and available, although diminished, energy.

It is then and there that purposelessness - perhaps the gravest of all human afflictions - can set in. It will, in fact, set in, unless the vacuum of lessened commitment is filled by a pursuit of new interests and voluntary activities.

In the absence of proactive effort, that void will be filled by gradual transition from a useful life to a purgatory of old farts (fastidious editors may choose to substitute "old you-know-whats"), wherein they barely justify the oxygen they consume.

While that pejorative label is offensive to many of my peers, I find it a remarkably accurate analogy, since the worst examples of that genre make their presence unpleasantly known, but contribute nothing to the well-being of those around them.

It's true, as the old saying goes, that youth has its privileges, and thus will it always be, but it is equally valid to say that maturity (as good a euphemism as any) has its obligations, one of which is to have a purpose in life, a justification for existing and a willingness to contribute something of value to society.

Another obligation of equal importance is to have a feeling of self-worth, to which rocking chairs park benches and TV remote controls are non-contributory. Neither is being an unnecessary burden to younger people or a source of annoyance to society in general.

Granted, there are no more mountains to climb or dragons to slay, but that doesn't grant a license to do nothing, and if idleness is seen as a well-earned reward for one's productive years, it is potentially as rewarding as an aggressive tumor.

Orchids to those of my approximate vintage (+/- 76) who productively participate in the work force as supermarket baggers, crossing guards, hospital volunteers, library assistants, theatre ushers, teachers' aides, security guards, political activists, child-care providers and other less-than-earth-shaking occupations, whether or not for compensation.

Blessed, too, are they who make use of their accumulated wisdom, experience and perspective by pressuring politicians to do what's right, sending letters and e-mails to editors and opinion shapers, participating in community affairs and generally making their feelings known to those in a position to make the world a better place - however minimally.

There's gray matter under that gray hair, and potential gray power in public affairs, if we oldsters opt not to sit on our assets, but instead put some polish in those golden years by rediscovering our "raison d'etre" and start living the lifetime that begins this very day.

Go, Geezers!