IS THE ECONOMY in a pause? If so, does it mean an economic slump? Or is it merely a "mini-pause," and therefore a good sign? The answer from economists, you will not be too surprised to read, is yes - and then again, no.

But something of significance seems to be going on, revealed by the fact that manufacturers' stocks climbed $2.1 billion in May, the fifth monthly increase in a row, and the largest in two years.

When factory inventories start to accumulate, it's a tell-tale sign that businesses are producing more than their customers are buying.

"Not particularly encouraging," was the verdict rendered by Commerce Department economist Courtenay Slater. "Things look pretty flat. You like to see things going up in a growing economy."

Commerce Secretary Juanity Kreps reminded this reporter that the economy later this year and in 1978 may get a lift from the jobs and public works part of the Carter stimulus package. But right now, she says, " I don't see any source for a pickup" in the crucial area of business investment, except a psychological lift if tax reform proposals seem to be making headway.

Carter administration officials have assumed right along that 1977's second-half pace of activity would be slower than the first. The unanswered question that seems to be developing is whether the current "flat" period cited by both Kerps and Slater will turn into a decline.

Economic Council Chairman Charles L. Schultze doesn't think that's going to happen. "The statistics in June do make you reflect," he said in a telephone interview, "but I wouldn't call it a 'pause,' if by 'pause' you mean a growth rate sharply flattening to a very low number in the second half of the year."

IF THE PAUSE turns into something worrisome, a stubborn inflationary trend will be assigned much of the blame. Gary Wenglowski fo Goldman Sachs notes that, with a 6 per cent inflation rate, federal tax laws automatically reduce real consumer income by about $7 billion a year, at present income levels.

The divergence in viewpoint among the experts is seen, as well, at the Federal Reserve system. At the May 17 meeting of the policymaking Federal Open Market Committee, there was a clear split. Beatish members worried openly that the economy is repeating its 1976 pattern, when inventories piled up, forcing a curtailment in production and a rise in unemployment.

More hopeful FOMC membbers predicted that expansion "in the quarters immediately ahead" would be stronger than expected.

On the optimistic side, Citibank's "Economic Week" letter acknowledges a decline in May's leading indicator index, but says that is "not enough to suggest the economy is headed for trouble."

Other measures show that "the economy is still healthy," Citibank's letter says. "Price increases have slowed, retail sales have held up and industrial production has soared."

The most pessimistic private forecaster appears to be Michael K. Evans of Chase Econometric Associates, Inc. He says that "the U.S economy is begining its slide toward a growth recession in 1978."

A growth recession is one in which the gross national product doesn't increase enough to provide jobs for an expanding labor force. Evans put real GNP growth at no more than 2 per cent in 1978 (compared to the Carter expectation of 5 per cent).

He predicts that unemployment - which edged up from 6.9 per cent in May to 7.1 per cent last month - will rise to 7.5 per cent by the end of this year, while the administration is sticking to its forecast that the jobless rate will be 6.5 per cent or less at the end of the year.

A MAN IN THE MIDDLE is Otto Eckstein of Data Resources, Inc., who says flatly that "the economy has entered a pause." But Eckstein can't decide whether it is a "momentary hesitation" or something "more dramatic." Give it another four weeks, and one can tell better, Eckstein suggests.

The basic negative signs that Eckstein lays out are the inventory pileup, the fact that the real volume of retail sales hit a peak in March and is "edging sideways since," no gain in the shipments of non-defense capital goods: and "surprising ease" in financial markets.

On the other hand, his analysis also shows many plus signs, including rising federal spending, and prospects that the potentially frightening U.S. trade deficit will shrink, aided by a sharp revaluation of the Japanese yen.

"In summary, the available evidence leaves no doubt that at the very least there is a mini-pause," Eckstein says, trying to balance it all out. "That is sufficient to mark down the risks of a boom-dust developments . . . Little pauses are to be expected in a recovery that is meant to be sustainable over quite a few years."