After White House Chief of Staff James A. Baker III appeared last week before the Senate Finance Committee in his quest to be secretary of the Treasury, Sen. Malcolm Wallop (R-Wyo.) lamented that he liked Baker but wasn't quite sure what he stood for.

The economic philosophy that Baker outlined, Wallop complained, was, "sort of tapioca: an undefinable sweet, thick fluid surrounded by equally sweet, squishy lumps that when you finish it you find it totally unsatisfying."

Wallop as well as others at the hearing were hungry for more indication of what Baker plans when he switches from what Sen. John Heinz (R-Pa.) called "the second-toughest job to the second-most-important job in America."

Baker gave few details of what the administration plans to do about high interest rates, Third World debt, the trade and federal budget deficits and tax reform. He was not even asked about many of the issues he will confront as the president's chief economic spokesman.

Political observers say it is not unusual for Cabinet-level nominees to avoid making waves or making their opinions known until after they are confirmed.

If he had given details, Baker could be held accountable for statements such as those made by Treasury Secretary Donald T. Regan at his confirmation hearing four years ago.

Regan said then that an expected $60 billion budget deficit would be eliminated by the end of Reagan's first term and predicted there would be a recession in 1981, but said there was "no sense of urgency or emergency about it."

The major point Baker made was that the administration's two top priorities this year would be deficit reduction and tax simplification. Baker provided no specifics on how those goals would be accomplished.

Baker said he didn't know what he would do about intervening in foreign currency markets where America's allies have become concerned about the high value of the dollar and its effect on their economies.

Baker was not asked about the Third World debt issue and was barely questioned about international finance -- the subject that committee members believe is his weak point. He said he would look at the Treasury's policy against intervening in foreign exchange markets. "I should not express, nor do I have an opinion on, whether our policy . . . should be changed," Baker said.

Baker said he hoped to have a close working relationship with the Federal Reserve Board, despite often stormy criticism of the independent body by Regan. But he had no opinion on a low-level Treasury department study on eliminating the independence of the Fed. "I formed no opinion with respect to whether or not there ought to be changes in the relationship, except perhaps that the term of the chairman of the Fed should be made coterminate with that of the president," Baker said.

Nor was Baker asked his views on the economy, his interest rate outlook or his opinions about a recession or further economic growth.

But he was clear on two points: His views will be those of the president, and the president's economic policy priorities this year will be deficit reduction and tax simplification.

"My views are those of the president," Baker told the Senate Finance Committee. "His views are that these are equal priorities on the domestic agenda; that is, tax fairness -- tax simplification on the one hand and deficit reduction on the other."

Many on the Senate Finance Committee disputed the equal weight given by Baker to tax simplification and budget cuts, saying that deficit reduction was by far the higher priority. Baker said only that the administration hoped to have $50 billion in spending reductions in the fiscal 1986 budget and had not abandoned its goal of reducing the budget deficit from 4 percent of gross national product to 2 percent by 1988.

The committee members also expressed doubts about the feasibility of the Treasury tax reform proposal in what could be characterized as the first congressional assault on the tax reform plan. Baker repeatedly told the senators that the Treasury tax reform plan would be changed and that it was only a starting point for the tax simplification debate.

Baker appeared sympathetic to the senators' complaints about the Treasury's tax proposal; he promised to look at provisions they alleged would hurt savings, investment and capital formation. Proposals that drew the most criticism included elimination of preferential treatment of capital gains, and repeal of the accelerated cost recovery system (ACRS) and the investment tax credit.

Baker specifically said he would look at elimination of preferential treatment of capital gains. Administration observers have said that Baker probably will consider also Regan's proposal to eliminate the fast business tax write-offs of the ACRS and the investment tax credit.

Baker, a Texas lawyer, was asked about Treasury's plan to shift the tax burden away from individuals and toward corporations. Baker said such a shift might be necessary to make the tax code simpler and fairer, but he added that he didn't "want to be understood as embracing the extent and degree" that the Treasury plan weights the shift.

Several senators said they were concerned that by not endorsing a specific tax simplification plan, the administration was causing many businesses to put off important investment decisions.

"Well, I think there is a problem with respect to the Treasury plan and the impact on investment decisions in some areas of business," Baker said. "Now, I'm not sure how severe that is."

Baker said that he had gotten complaints about the uncertainty over tax simplification while at the White House, and that the Treasury Department had assured the business community that ample adjustment time would be given.

"I think it's something that perhaps deserves a further look," Baker said. As soon as he becomes Treasury secretary, he said, "I plan to take another look at that and see if there's something that should be done concerning a statement about" whether the tax proposal would be made retroactive.

On the trade deficit issue, Baker said it was "a serious problem" and that the administration is working with the Japanese government on a new round of trade liberalization initiatives.

"We think that if we're successful in dealing with the budget deficit and we reduce the size of that deficit on the spending side, that should hopefully help with the trade deficit because it should permit some" decline in the dollar, he said.