The fact that Shakespeare’s plays still feel so relevant 400 years after his death says something both reassuring and distressing about human nature. On the darker side, Philadelphia Shakespeare Theatre Artistic/Executive Director Carmen Khan points out, “[One of the murderers] in Macbeth basically says, ‘I’m so wronged by the world that I’ll do anything to destroy it.’ My god, that’s ISIS; that’s Donald Trump. People are so angry that it sounds like a modern sentence.”

That’s one reason why Khan decided to balance the tragedy of “Macbeth” with the comedy of “Twelfth Night” to open PST’s 20th anniversary season, which also marks the four centuries that have passed since the Bard’s demise. “As an actor you can get really depressed just doing ‘Macbeth,’” Khan admits. “It’s kind of refreshing if you have the chance to also focus on a drunken revel of a play.”

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“Macbeth” opened the season last week while “Twelfth Night” will open on April 14, with the two plays running in repertory through late May. Khan hopes that audiences will return for both plays and enjoy the offbeat experience of seeing the conflicted Macbeth transform into the stern Malvolio, or the mischievous Sir Toby Belch become the heroic Macduff.

Aside from their opposing moods, however, Khan sees more similarities in the two plays than a casual viewer might expect. “These plays express two sides of who we are as humans,” she explains. “They’re all about regret, the mistakes you make that you can never change. ‘Macbeth’ encapsulates that in a tragic way, and then ‘Twelfth Night’ shows us in all our foolishness.”

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Spending two decades exploring the work of a single playwright inevitably leads to those sorts of insights. PST’s anniversary season was designed to reflect the growth that has taken place in the company and its founder over those years. “Macbeth” was one of the first plays produced by the company, while “The Merchant of Venice,” which will close the season this fall, is returning to the Philadelphia Shakespeare Theatre mainstage for the first time in 20 years.

“I think what Shakespeare has tapped into in an encyclopedic way is our very humanity,” Khan says. “He’s this incredible symphony of human feeling. After 20 years looking at this 400-year history, I feel like we have a little insight into what they’re really about, but you never stop learning.”

IF YOU GO
Macbeth / Twelfth Night
Through May 22
The Philadelphia Shakespeare Theatre
2111 Sansom St.
$20-$45, 215-496-8001
Phillyshakespeare.org