One knows one ought to catch up on Shakespeare, but one hasn't even finished "The World According to Garp" yet, and life marches on so quickly nowadays.

Mastercharge becomes Mastercard without warning, and currency is all.

There is an active life to be lived here around the capital, and one knew Rep. Bumwhistle before there even was an Abscam, and is surprised by little. Dustin Hoffman is a shoo-in for the Oscar after "Kramer." Hostages Never Have a Nice Day. Have you heard? Marcia is learning Navajo.

The thing to do is reread all of Shakespeare, in sequence, during the upcoming sabbatical to Patagonia. Holinshed's Chronicles, too. Art must be tended carefully, lest it wither.

One is no fool.

Or is one?

Tonight at 8 o'clock on public television (Channel 26), the BBC and Time-Life Television presents Shakespeare's "Henry IV, Part I," the play that introduces Falstaff; the play in which valiant, bullheaded Hotspur dies under Prince Hal's calculating sword, and in which doom stalks closer to the Fourth King Henry, usurper of tortured Richard II's crown.

It is a production that fills the small screen with fine performances, bereft (by the microphones and closeups of TV) of needless shouting, yet so resounding with laughter, horror, amazement, tragedy, politics and greed that it rings like a bell struck by lightning.

Garp can wait.

The Shakespeare Plays, as the series is called, left off last year with Richard II, which was then repeated two weeks ago.

Now Henry Bolingbroke, seen then as the deposer, reappears as king, and a man who is having trouble with the family business, which happens to be running England.

His older son, Hal, is supposed to be preparing himself for monarchy as heir apparent, but instead has taken to lying about, drinking sack and playing practical jokes on a great tub of lard named John Falstaff, whose court is the Boar's Head Tavern. Anthony Quayle as Falstaff is fine, all blubber and sophistry as required, but trenchant and effective in his character's suddenly philosophic asides.

King Henry, played by Jon Finch, looks admiringly on the son of a family friend -- Henry Percy, nicknamed Hotspur for his temper -- and seems ready to adopt him in Hal's place. Hotspur loses points, however, when the king learns he has joined a plot against the throne.

Hotspur's fellow plotters are a loony Welshman, Owen Glendower (played amusingly by Richard Owens) and the Earl of Worcester, who Clive Swift has successfully given the manner of a bad-hearted businessman. Together they plan to defeat Henry and divide up England among themselves.

When push comes to shove, on the bloodstained and wordy battlefields for which Shakespeare is known, Hal comes to his father's side, armor shining and the incumbent administration carries the day. Even Falstaff, for whom cowardice is a way of life, finds his moment of carnival glory.

This understated production brings out everything that need be hoped for: Tender moments between man and wife; a lovely song in impenetrable but hypnotic Welsh; vast edifices of hilarity that crumble into death and moral ambiguity; the elusive characterizations in which lie the play-wright's genius, the battlefield scenes of majestic slaughter and crushing impact.

Shakespeare's battlers fight as much with words as with swords, but when two of his combatants' sentences clang together in the field, they sound the drama of war more frighteningly than all the wing-camera footage of "Tora, Tora, Tora."

In the end, the good guys win -- but something is skewed. King Henry is a bit coldblooded all the while, and son Hal, by all rights a hero and a changeling, leaves an acid taste.Is Falstaff his friend, or dupe? Who is the more honorable: Hotspur, dead by his own intemperate adventure, or Hal, a survivor, plotting his course to kingship with frosty logic? Occasionally, Falstaff -- an unconscientious ojector in the war of honor -- makes the most sense, but he is without doubt a murdering scoundrel.

These are puzzlements not found on "Love Boat," nor in Garp, either. But the characters carry on through two more plays, where further answers lie. b

There are a few small factors to consider before inviting the neighborhood over for 2 1/2 hours of public TV night.

One is that Shakespeare, like Beethoven, was not much for exciting titles.

"Henry IV, Part I" is undoubtedly the least-boffo name ever given a drama, however fine it may seem after the fact. If Margaret Mitchell had named "Gone With the Wind" "Annals of Atlanta, Section A," there would not be an MGM today.

And it happens that this play, in this production, takes about half an hour to build. By the time Falstaff makes his second entrance, early in Act II, however, the plot has been explained, the characters filled out and the Elizabethan cadences gotten used to. Thereafter no one will be tempted to ask what else is on.

The BBC and Time-Life are in their second season of a six-year project that will eventually bring to television all of Shakespeare's plays. This one is one of the most familiar and least difficult.

By the time all 37 have aired, we will be ready to start again.