The Quincy-Holmes Arts Festival opens this evening with a panel discussion on the case for public support of the arts in the Quincy Dining Hall at 8:30 p.m. Conductor Leopold Stokowski is a member of the panel, which also includes Norman Singer, director of the Aspen (Colorado) Music Festival, and author Dean Brelis.

Sarah Caldwell, director of the Boston Opera Group, will begin the discussion with a paper. Daniel Seltzer, assistant professor of English, will moderate.

Tonight's panel is the first in a series of three discussions on the present system of financing the arts with private resources and proposals for government grants to provide further support.

Tomorrow evening's session will hear a paper by Daniel Robbins, assistant curator of the Guggenheim Museum, on what type of art and artists the government should assist. Machinery for government aid to the arts will be discussed by the Saturday aftersoon panel, which includes Joseph Papp, producer of the New York Shakespeare Festival.

Besides the symposium, the Arts Festival includes a jazz concert tomorrow afternoon and a chamber music recital in Holmes Hall on Sunday afternoon.