The new Mirror Theatre offers two fine works from the past

The Mirror Theatre is located at a place called the Real Stage - which may look like a contradiction in images. It is not. As a statement in an introductory program note explains, the new company on West 46th Street embraces Shakespeare's ideal of playmaking - ''to hold, as 'twere, the mirror up to nature.'' It is an ideal to inspire one of the most challenging of stage enterprises: the founding of a repertory theater.

The Mirror Theatre has inaugurated its alternating program with Susan Glaspell's ''Inheritors'' (1921) and Clifford Odets's ''Paradise Lost'' (1935). To quote a further program note: ''These plays are intended to be seen together. Both plays were controversial in their time.''

The two dramas share an additional similarity. Both failed when first produced. ''Inheritors'' subsequently became a standby of Eva Le Gallienne's Civic Repertory Theatre. Odets campaigned fervently to save ''Paradise Lost,'' the work he cherished so much and on which the Group Theatre counted so heavily. After the play's failure, the disillusioned dramatist accepted his first Hollywood assignment, the screenplay for ''The General Died at Dawn.'' There has been no New York production of ''Paradise Lost'' since its 1935 premiere.

The Mirror Theatre's opening bills are important both for their awareness of theatrical history and for the artistic integrity with which they have been mounted under John Strasberg's direction. ''Inheritors'' sprang from the era of 1914 to 1921 - a period when authentic patriotism degenerated into chauvinism and inflamed paranoia. Miss Glaspell assailed what she saw as the evils of a corrupted idealism.

The action of the play occurs at a Midwestern college, the land for which was given by a visionary pioneer. Instead of becoming (in Emerson's phrase) the lengthened shadow of a man, the institution has declined into an academic preserve more concerned with its economic self-preservation than with freedom of expression and democratic rights.

The heroine of ''Inheritors'' is Madeline Morton (Sabra Jones), the granddaughter of the original benefactor. At the certain risk of being abandoned by her family, Madeline accepts the harsh legal consequences of a spontaneous act in defense of human rights. Contrived and obvious as it may seem today, ''Inheritors'' involves recognizable people in a genuine ethical conflict. One of the virtues of the revival staged by Mr. Strasberg is the respect with which it approaches the text and its period.

''Paradise Lost'' was Odets's ambitious attempt to analyze - in a discursive, somewhat Chekhovian manner - the effects of the depression years (1932-35) on a middle-class Jewish family. Like ''Inheritors,'' it concerns an aspect of the struggle to preserve some of the ideals of the American dream. In their quite different ways, Madeline Morton of ''Inheritors'' and Leo Gordon (Bryan Clark), the embattled small-business man of ''Paradise Lost,'' face their respective ordeals with courage and an inner conviction that sustains them.

The Mirror Theatre ensemble already displays the kind of potential that augurs well for the goals of repertory. Among the actors appearing in the first two plays are Geraldine Page (billed as artist-in-residence), David Cryer, Clement Fowler, Maxwell Caulfield, and Tom Brennan. The 30-member company also includes Juliet Mills and Mason Adams. Set designer Ron Placzek makes resourceful use of the Mirror Theatre's small stage. The productions are lighted by Mal Sturchio and costumed by Heidi Hollmann.

''Inheritors'' and ''Paradise Lost'' will be followed into the repertory by ''The Hasty Heart'' (1945), by John Patrick; ''Rain'' (1922), the John Colton-Clemence Randolph adaptation of W. Somerset Maugham's ''Miss Thompson''; a new translation of Ibsen's ''Ghosts'' (1881); and the New York premiere of ''Sore Throats'' (1979), by British playwright Howard Brenton.

The Mirror Theatre was founded early in 1983 by Mr. Strasberg and Miss Jones (Mrs. Strasberg), the company's artistic director. Initial funding of $300,000 came from Laurance S. Rockefeller, the principal benefactor, the Vincent Astor Foundation, Lila Acheson Wallace, and other contributors.

The 80-seat playhouse occupies the reclaimed third floor of a nondescript building on 46th Street west of Eighth Avenue. The premises are unprepossessing, but the air of dedication is unmistakable. And so are the founders' purposes: ''(I) To present dramatic literature of all periods, including new plays. (II) To select a season of plays that promote active thought. (III) To select plays that reveal positive unifying elements in an age of possible nuclear warfare. (IV) To go below the surface of life to the essential passion of living and celebrate life.''

High aims for a loft space.