The point man for US domestic policy

President Reagan detailed his own policies in his State of the Union speech. But someone had to dig out the views of Mr. Reagan's top people and put them together for the chief executive to accept, reject, or refine.

Edwin L. Harper is that ''someone'' - on the domestic-policy side.

You hear a lot about the President's key assistants - Messrs. Meese, Baker, Deaver, Clark, and Stockman. As the President's chief domestic-policy adviser, Mr. Harper also is in a position of major importance and influence.

But presidential policymaking takes place behind the scenes. And Harper, with a particularly unassuming and quiet demeanor, seems fitted for the anonymity that goes with the job.

For an hour the other morning, Harper gave reporters what might be called a seminar on policymaking in the White House, together with what he regards as presidential views on a number of important issues. Excerpts from the exchange follow:

You are the President's chief domestic-policy adviser and have been for some time now. Where is your advice showing up?

Well, it is showing up when the President issued his State of the Union speech and in the fact sheets issued afterward. And I think in the next few weeks you will see a number of initiatives that have been developed over the last six months.

I took on the job as assistant to the President for policy development about a year ago. Part of the job description then was to develop the midterm planning process and make sure our agenda and program were in place for the last two years of the President's first term.

Our target was to get these decisions through the Cabinet counsel process and get our homework done, so that by the time the final budget decisions had been made and the State of the Union (speech) had to be written, we did have this work done and the President had an opportunity to choose, to set priorities. . . .

For example, reinforcing the economic recovery program with the Employment Act of 1983 is one of the products of that policy-development process. Another example is the President's new trade strategy: combining free trade with a fair shake for America's farmers and workers. Another example is the President's proposal for education for the long term which contributes to a stronger work force in America and makes us more competitive.

The President's call for a national commission on industrial competitiveness, the health-care reforms that make sure that costs of health care in America do not go through the roof and make it unaffordable, these are additional highlights of what have been developed in the last few months.

How many new jobs will come out of the President's employment initiatives?

Well, if by creating jobs you mean those that will come from the new water projects built into the budget and a tre-mendous increase in highway construction for repair and maintenance built into the budget you are welcome to count them. . . . I think the more legitimate economic justification for those programs is that we need to protect and maintain the infrastructure of this country - and that will increase our productivity. Real jobs for the long haul are created by the private sector.

How does your legislation help someone who has been laid off, say in the copper industry?

. . .First of all, there is (in our legislation) the extension of unemployment insurance benefits that would help those who have been unemployed for a long period of time. Second, the wage voucher or wage tax credit is designed for just such a person - whose career may have been in the copper industry and who says, ''I don't see any future in the copper industry and what I really should be doing is something else.'' So that person can go to another employer and say, ''Look, I want to go to work in your industry. Instead of taking an unemployment check, I'll come to you and the government will give you tax benefits to hire me and train me and get me up to speed so that I can play a useful role.''

When the President in the State of the Union said, ''We who are in government must take the lead in restoring the economy,'' what did he mean?

He sees a clear and important role for government in defense; in protecting . . . the truly needy. . . .