Sometimes a great television show bursts forth fully formed, like “The Sopranos” or “Lost” – epic journeys into the heart of the human condition that astonish us immediately with their dexterity of language and storytelling. For other shows, it takes a while. Episodes, if not seasons, go by before the writers even see for themselves the forward momentum in the characters they have created. If an audience (and a network) is patient, there can be huge artistic rewards when, at last, a series summons all of its potential and delivers an episode – or a season – in which all is synthesized and perfected. When that moment comes, those of us who watch television as a refraction of our own lives feel vindicated by our faith in a medium that so rarely delivers on its promise.

The rewards come so fast and furious in the final season of “Six Feet Under” that you’ll barely have time to catch your breath. I’ve never experienced anything quite like the exhilaration of watching the first four episodes (they begin airing next Monday night at 9 p.m.); they connected to primal emotions about love and marriage and death, and pushed me to think about life – my own – in ways no television show has ever quite done before. No amount of appreciation for this HBO series will prepare you for the huge leap forward taken by its writers and actors this time around; even if you’ve doubted your devotion in seasons past, allow yourself the chance to return this season with an open mind. It won’t be long before it sweeps you up in its powerful emotional wave.

The Fisher family finds itself splintered as never before. Every relationship hangs on a rocky precipice; every line leaves another unspoken. As before, the marriage of the matriarch, Ruth, to the deeply unstable George Sibley has an air of impending doom around it – his electroshock treatments have left him a pained, morbid shell, and her an angry, bitter woman still searching for comfort through knitting and neediness. The arrival this season of George’s daughter, Maggie, as a regular suggests yet more complications for the Fishers. She quickly creates a tender relationship with Nate that seems sure to shake up his stormy marriage to Brenda. Claire and her mother have reached an apex of opposition; every interaction comes at a mega-decibel pitch, and their resentments become intractable. (Claire’s relationship with Billy suffers repeated testing, too, particularly when he adjusts his lithium levels.) Even Rico Diaz, the Fishers’ business partner, loses control over his relationships – and his senses – as he explores the single life with desperation and doubt.

If there’s a weakness in this neurotic ecosystem, it’s in the ongoing tribulations of David and Keith. They seem to be circling the same issues that divided them in season one – fidelity, family, and their future. How many times can we watch these two men battle, then kiss, then battle, then kiss? Their endless forgiveness feels like the single false note in a symphony of truth. But whatever the failings of single moments, the first four episodes stand as triumphs of structure, writing, and direction. There are moments of “Six Feet Under” this season that no human being with a beating heart will be able to watch without feeling it break.

***

At first, you might think the improvements in “Entourage” this season stem from an effort to make the show more like “Sex and the City” – and there’s no doubt a little of that show’s same-sex camaraderie has crept into the concept this time around. In the first episode, the boys prepare for a pajama party at the Playboy mansion with all the giddy excitement of HBO’s comedy gold standard. But it cheapens the efforts of the “Entourage” producers to suggest that its improvements owe themselves to imitation. “Entourage” has transformed itself into a smart, probing look into Hollywood behavior that makes it essential viewing this summer – and it has done so by adding a level of sophisticated storytelling to its glitzy, shimmering artifice.

Last season “Entourage” (returning this Sunday night at 9:30 p.m.) struck me as too infatuated with itself; the only fun I could find was in Kevin Dillon’s character, cursed with the burden of being the failed older brother of a young, studly success. The whole notion of this gang of buddies sucking off the nipple of celebrity – and of us enjoying the view – seemed a little nauseating. It was written by insiders stepping outside and looking back in through the keyhole, a pointless exercise that subtracted from our understanding of human nature, not to mention the movie industry.

I always suspected the “Entourage” writers knew better, and it turns out they did. This season they have added a full dimension to their story, and now there’s a reason to keep watching every week. Vincent Chase, the hunky star whose career trajectory now keeps “Entourage” humming, has been offered a superhero role – “Aqua Man” – that he doesn’t want; he’d prefer to keep doing low-budget indies and maybe a play or two. He finally bows to pressure and accepts the part, only to discover – in a plot twist I won’t disclose – that “Aqua Man” may no longer belong to him, for reasons that speak to the scary truths of Hollywood behavior. It’s a must-see intersection between drama and real life in a show that has finally found its voice. Plus there’s a cameo by “Full House” dad Bob Saget that’s so frighteningly real that we all must pray that it isn’t, for the sake of children everywhere.