Natural gas deregulation, despite the near theological rhetoric used by opposing forces in the often acrimonious Senate debate over the last few weeks, has always come down to a battle of numbers. Both sides offer different answers to the question Energy Secretary James R. Schlesinger Jr. says is central: "How much is enough?"

Schlesinger and other opponents of the Pearson-Bentsen bill, which would deregulate almost all natural gas prices in five years, are quick to reel off figures indicating that higher gas prices in the past haven't resulted in increases in supply. The Pearson-Bentsen bill was passed yesterday by the Senate on a vote of 50 to 46.

Since 1972 the federally regulated selling price on interstate gas has risen from about 26 cents per thousand cubic feet to $1.47, yet reserves have declined by 19 per cent, and natural gas production has dropped by 12 per cent.

"That's a seven-fold increase in five years, yet each year they (the oil industry) come back asking for more," Schlesinger said.

Central to the Administration argument is Schlesinger's assertion that there is little supply elasticity in natural gas pricing - higher prices, in other words, would not result in significant increases in natural gas reserves, which have been declining each year since 1967.

In July the House passed President Carter's natural gas proviso nearly intact. It would raise the current $1.47-per-thousand-cubic-feet price for new gas to $1.75, the energy-equivalent price of fuel oil.

Gas prices would be allowed to rise roughly 10 per cent a year, to match increases in world oil prices. The House also extended federal controls to the unregulated intrastate gas market, where new gas sells typically for $2.50 or more per thousand cubic, and adopted Carter's definitions of "new" gas as gas discovered after April 20, 1977.

Other deregulation opponents, including Ellen Berman of the Consumer Federation of America and James Flug of Energy Action, a consumer group that advocates breaking up the oil companies, say the central political question is not higher prices and new supplies - but industry profits.

"Deregulation will take the industry from outrageously high profits now to more outrageously high profits," Berman said, pointing to the 445 per cent jump in gas prices since the early 1970s.

Flug said that if a variation of the Pearson Bentsen bill is enacted."The companies will have to withhold gas supplies to avoid reaping embarrassing profits."

The industry disagrees.

Oilmen have targeted their greatest lobbying efforts at deregulating natural gas, according to Standard Oil of Indiana chief economist Ted Eck, "because that is where the best chances are for new supplies and new revenues."

Eck and others say that phased-in deregulation will result in 3 trillion cubic feet in added production by 1985.

As expected, there is a sharp divergence between administration and industry estimates of what would happen to gas revenues if prices are deregulated. Eck says the plan offered by Sens. James B. Pearson (R-Kan.) and Lloyd M. Bensen (D-Tex.) would result in only $6 billion in additional revenues over the Carter plan by 1985.

Yesterday, White House energy officials said that under the House Passed Carter plan, the oil industry would garner $15.3 billion in additional natural gas revenues in 1985.

David Foster who heads the Natural Gas Supply Committee, which has a $600,000 annual budget to lobby fulltime for gas deregulation, maintains that gas deregulation ultimately would result in billions of dollars in consumer savings because new gas supplies would replace higher-cost synthetic fuels. Other industry executives, however, are reluctant to embrace publicly the gas deregulation consumer savings argument.

One thing is certain: no matter what kind of compromise measure the Senate agree upon, natural gas prices will go up.

A September Congressional Budget Office study estimated that under Carter's plan a typical home heating bill would rise from $42.80 per month to $47,20 by 1985. Under full deregulation, the 1985 monthly heating bill would rise to $70.