'Nickleby' and humanity's unfinished business

In addition to all of its other remarkable features, ''The Life and Adventures of Nicholas Nickleby'' can claim to be Broad-way's only current play of social significance. That may stand both as a comment on the theatrical times and a further tribute to Charles Dickens. Certainly it adds testimony to the breadth of Dickens's vision and the depth of his social concern. The play's relevance for today ranges from amusing trivia to matters of justice and equality with which society is struggling a century and a half after the novel was written.

Consider, for instance, the tragic problem of child abuse. In the week that ''Nicholas Nickleby'' opened at the Plymouth Theater, the top official of this city's Commission on Child Abuse and Neglect told the New York Post: ''We are losing the battle against child abuse. We are losing an average of two kids a week to abuse or neglect.''

Surveys and findings by private and government agencies confirm the seriousness of the crisis nationwide. The cruelties of Dotheboys Hall, a specimen of the notorious Yorkshire schools against which Dickens campaigned so effectively, have disappeared. But the horrors of child victimization within the family, and to a certain extent in institutions where minors are housed or detained, has not ended. Existing reports show that, particularly in home situations, reported child abuse has increased sharply in recent years in the United States. The positive side of the picture is that both government departments and private guardians of child welfare are intensifying efforts to combat these evils.

''Nicholas Nickleby'' also reflected a concern for women's rights. When Madame Mantalini, the industrious dressmaker married to a squandering scoundrel, tries to claim her business, she is curtly informed: ''A married woman has no property.''

Both England and the US have long since enacted married women's property acts to correct the earlier wrong. Yet according to Phyllis Segal, legal director of the Legal Defense and Education Fund of the National Organization for Women: ''There are states where limitations to women's property rights still exist.'' Nor should it be forgotten that the republic which considers itself a model of enlightened democracy is still three states short of ratifying the Equal Rights Amendment to the Constitution.

There are other social, political, and even international questions on which ''Nicholas Nickleby'' has pertinent things to say. Expressing a sentiment not unworthy of certain latter-day national leaders, one character in the play exclaims: ''The Russian bear is pawing at the very vitals of the empire.'' As for politics, the satirical scene with Mr. Gregsbury, member of Parliament, is a hilarious example.

''He was,'' writes Dickens ironically, ''a tough, burly, thick-headed gentleman with a loud voice, a pompous manner, a tolerable command of sentences with no meaning to them, and in short every requisite for a very good member indeed.'' (Dickens had been a parliamentary reporter.) When a delegation of constituents demands Mr. Gregsbury's resignation because he has not kept his campaign promises, ''the great M.P.'' imperiously refuses - ''moved only by high constitutional considerations which I will not attempt to explain.''

The launching of the United Metropolitan Improved Hot Muffin and Crumpet Baking and Punctual Delivery Company may not have a literal equivalent in today's stock promotion hyperbole. But in addition to its reference to the speculations that preceded the great crash of 1825/26, this remarkable enterprise also constituted the very model of monopoly. The second resolution passed by the company's founders recognized the expediency of abolishing ''all muffin (or crumpet) sellers, all traders in muffins (or crumpets) of whatever description, whether male of female, boys or men, ringing bells or otherwise.'' What price competition? Happily, the actors still give out free muffins at the Plymouth.

Broadway economics has provided ''Nicholas Nickleby'' with one of the biggest responses to a text slightly amended for American consumption. Whereas at London's Aldwych Theater, tickets to the show could be bought for as little as the equivalent of $10, all seats to the New York production cost $100 (for the two-session marathon), a Broadway record. When Vincent Crummles, the expansive actor-manager, tells Nicholas he is sailing for America to better his fortunes, he adds by way of explanation: ''I have it on the best authority that they will pay anything.''

Local audiences good-naturedly roar with laughter.

''Nicholas Nickleby'' is nowhere more moving than in its final scene, one of the few passages invented by adapter David Edgar. Upstage, the benevolent Cheeryble brothers, their guests, and the now united lovers are celebrating Christmas. As they and the whole company of actors observing the scene raise their voices in ''God Rest Ye Merry Gentlemen,'' a forlorn figure downstage is picked out in cold white spotlights. He is one of the runaways from the now defunct Dotheboys Hall - lying frozen in a snow-covered field.

Nicholas walks forward, picks up the inert form, and - as the caroling swells - stares at the audience with a look of deep pain and sadness. The contrast between the hard-won joy of the celebrants and the manifestation of man's inhumanity to the defenseless is more than a striking theatrical effect. It is a stark reminder of humanity's unfinished