Beneath the photograph, the advertisement's text begins: "You never thought you'd see a toilet quite like this." Actually, it looks like an orthodox toilet. Except it is sitting on the yellow line in the middle of a deserted Western highway. And behind it a woman shimmering in a silver gown, and hitchhiking. This toilet, the Kohler Company's pride and joy, is the San Raphael model, shown in "Swiss Chocolate"--that's the color, not the material. Welcome to the world of advertising, America's least understood big business.

In 1982, $67.3 billion was spent on advertising. The biggest spender, Procter and Gamble, spent upwards of $700 million. The biggest agency, Young & Rubicam, had U.S. billings of $1.6 billion. Critics of advertising often ascribe to it vast and unproven powers of manipulation. Such powers are an article of faith among critics of capitalism, who argue that big business can manage, even dictate, demand and hence is not disciplined by market forces. But now Daniel Pope, a University of Oregon historian, has published a clarifying book, "The Making of Modern Advertising."

Selling, he says, once was the storekeeper's responsibility. But modern manufacturers must sell as well as make products. The technology that made mass production possible made advertising necessary. It was necessary to generate strong demand for goods produced by capital-intensive industries with high fixed costs.

Railroads that could distribute goods nationally called forth advertising to stimulate wants. Advertising of national brands helped give rise to national magazines. A benefit to consumers was an economy increasingly based on high-volume production with low profit per unit.

Advertising promises a flowering of individuality as persons define themselves in choices. Yet advertising presupposes mass tastes. (Pope notes that at 9:15 p.m. EST, Feb. 5, 1982, Coca-Cola engaged in "roadblocking," buying time on all three networks to introduce its "Coke Is It!" commercials. That night four out of 10 Americans saw the commercials.)

Advertising promises a democratic distribution of pleasure, but sells many goods by stressing exclusivity--the idea that the purchaser will elevate himself above the herd. Advertising celebrates choice--"consumer sovereignty"-- yet stirs anxieties about whether human volition is sovereign over manufactured persuasion.

Advertising performs an--often minimal--informing function necessary for rational choice. But as Pope says, advertising ensures that consumers often are impulsive and suggestible. He says the average supermarket stocks about 10,000 different brands and products. If each customer bought only what he came to the store intending to buy, supermarkets would be very different. They depend on impulse buying. Some impulses are triggered by previous exposures to advertising.

One hundred years ago, Americans read advertisements just to ascertain the availability of goods to satisfy elemental needs--food, clothes, tools. Now they read advertisements to ascertain what they might decide they desire. Certain necessities (soap, toothpaste) are heavily advertised, but it sometimes seems that half the GNP is generated by personal anxieties--about bad breath, damp underarms.

McDonald's advertisements talk as much about convenience as about hamburgers: "You deserve a break today" or "We do it all for you." Those gorgeous "Miller time" commercials make no claim. They create a mood, and are weapons in a market- share battle. They do not aim to get you to buy a Miller beer rather than a Buick, or to make you thirsty, or to get you to buy Miller rather than Dr. Pepper when you are thirsty. They aim to get beer drinkers to drink Miller rather than some other beer.

Advertising is less a "science of persuasion" than an art of arresting attention briefly so that perhaps some commercially useful response will occur, sometime. Arresting attention is increasingly difficult as Americans become inured to sensory blitzkriegs. Print advertisements must be especially ingenious to seize the attention of persons saturated with sound and motion. So: put a toilet on a highway.

Bob Sievers is with the Campbell-Mithun agency in Minneapolis, Kohler's agency. Plumbing fixtures are, he says with some understatement, "a low-interest subject." If you just show a pretty bathroom, few eyes will pause. The toilet on the highway is an eye- catcher, all right, but to what end?

The aim is not to get Aunt Min to say to Uncle Ralph, "Hey, let's get a new toilet rather than a new Buick." Rather, the aim is to get people who must think about plumbing fixtures to think that Kohler is a company with snap, crackle and pop. Well, that is the least you can say for folks who name toilets "San Raphael" and "Rialto."