"He does not deserve the sweet who has not tasted the bitter." -- Erasmus

"I licked my finger and it tasted good." -- Schlatter

It has been 17 years since chemist James M. Schlatter, who was tinkering with an anti-ulcer drug at the time, dipped his finger into a mixture of asparatic acid and phenylalanine and, for reasons that remain unclear, brought the result into contact with his tongue. Now, after a long legal and scientific struggle, the stuff that was on Schlatter's finger that fateful day in 1965 can be on your finger too, or dissolved in your coffee, or stirred into your yogurt, or sprinkled over your cinnamon toast.

Aspartame is here.

Aspartame (retail name "Equal") is the last word--or, at any rate, the latest word--in artificial sweeteners. The aspartame equivalent of two teaspoons of sugar contains a mere four calories (as against 32) and, according to the manufacturer, "tastes nearly identical to sugar." When samples of a "powdered beverage" plus either aspartame or sugar were taste-tested by "a panel of mothers and their children inexperienced in taste-test techniques," the mothers, we are told, found both equally irresistible, and the children preferred the aspartame alternative "decisively."

And it is not only mothers and children who feel this way. Even former Secretary of Defense Donald Rumsfeld drops heaping portions of aspartame into his coffee. Rumsfeld, it should be mentioned, is the president of G.D. Searle and Co., which holds the patent on aspartame and has been in a corporate tizzy over it ever since staff chemist Schlatter reported his accidental discovery. Not even a brief scare about possible brain damage in rats (which led the Food and Drug Administration to send aspartame back to the lab for further study in 1974) could divert the people at Searle. They thought they had a winner then. They think so now. And the folks who make Lipton iced tea and Country Time lemonade, two of the first products that will be marketed in dietetic lines containing aspartame, think so too.

What should the consumer think? The consumer will perhaps be forgiven if, after all the other substitute edibles and potables that have been pitched his way over the years, from saccharin to methadone, he wishes to ask a few questions. Questions like: How do I know it's safe? How much does it cost? Is there a bitter after-taste?

The answers will be found below. But first, a question for the consumer:

Why?

Why, when it comes to matters of ingestion, do Americans think they can have everything? Why in this sweet land of liberty must there be a laboratory solution to every problem? Why, if somebody needs to cut down on sweets, can't he or she consider simply cutting down on sweets?

If that sounds harsh, it is nowhere near as harsh as the fate of the sugar-substituter. He has the worst of both worlds, keeping his addiction alive without ever fully satisfying it. He is trying to fool his own system, and insofar as he succeeds, he throws his mind and body into a perpetually hostile relationship. The tastebuds, after all, are the defensive radar of the digestive process. When they say something is sweet, they tell the body to expect a quick shipment of premium fuel, and when it gets something different, what's a body to think?

It is tempting, in these hard economic times, to applaud any new product unveiled by a domestic company, especially one located in the ailing heartland. But as it happens, G.D. Searle of Skokie, Illinois, has yet to produce any aspartame within our borders. It will be drawing for some time yet on a stockpile made in Japan, which thus stands to profit from yet another chapter in American self-indulgence. Meanwhile, our Caribbean neighbors, with their already-fragile sugar-based economies, stand to suffer. If aspartame is everything its makers say, President Reagan's Caribbean Basin Initiative could prove very timely indeed.

And aspartame is only one small breakthrough in the relentless American pursuit of the quick fix and the cheap thrill. While our competitors stride forward in steel and computers and robotics, we have become champions of the bullet-proof tomato, dietetic wine and mineral-water sprays for freshening the face. Only two months ago, the FDA purged the market of so-called "starch-blockers"--large-molecule forms of kidney-bean protein that, according to their purveyors, inhibit the body's ability to absorb carbohydrates, so we can have our cake and excrete it too.

But enough.

Now about that after-taste. G.D. Searle claims that aspartame has "no bitter or metallic after-taste," and an informal group of taste-testers surveyed for this article tended to agree. Unfortunately, they were not as enthusiastic about the fore-taste. They preferred Equal to existing artificial sweeteners. Some even found it indistinguishable from sugar when added to coffee. But others were dubious, and those who tried a sample of Lipton's aspartame-sweetened iced tea were positively scornful.

As for price: Aspartame costs more--several times more than saccharin, a shade more than sugar itself--but, according to Searle, "research has shown that the benefits . . . are perceived by the consumer as worth the premium price."

And safety: The two components of aspartame, aspartic acid and phenylalanine, are amino acids, which, as every former schoolchild knows, are "the building blocks of life." Could a building block of life be bad for you? Well, it could if you have the rare genetic deficiency called phenylketonuria, which affects one in every 15,000 infants. A warning label to this effect will appear on labels of all aspartame-containing products. Otherwise, to quote FDA commissioner Arthur Hull Hayes, Jr.:

"Few compounds have withstood such detailed testing and repeated, close scrutiny and the process through which aspartame has gone should provide the public with additional confidence of its safety."

When the FDA gave its final approval to aspartame last year, a few dissident voices inside and outside the agency called for further delay and a longer-range study. Now, of course, the study will be an open-ended one conducted in the population at large. Participation is voluntary.