Answer by Marcus Geduld, Shakespearean director, computer programmer, teacher, writer:
If anyone tells you there are objective standards, they're full of crap. This is a matter of personal taste. There are trends. There are many people who loved Philip Seymour Hoffman's acting. But if you don't, you're not wrong. At worst, you're eccentric.
I'm a director who has been working with actors for almost 30 years, and I'm the son of a film historian. I'll give you my definition of good acting. But I really want to stress that if I say, “Pacino is great,” and you disagree, my experience does not make me right and you wrong. It just means we have different tastes.
First, for me, an actor is good if he makes me believe he's actually going through whatever his character is going through. I'm talking somewhat about physical stuff (“He really is getting shot!” “He really is jumping off a moving train!”) but mostly about psychological stuff (“He really is scared!” “He really is in love!”). If an actor seems to be faking it, he's not doing his job.
Second, the actor has to surprise me. This is the most nebulous requirement, but it's important. Except for really small parts that aren't supposed to call attention to themselves (e.g., a bank teller who just cashes the hero's checks), it's not enough for actors to just seem real. Seeming real is a requirement, but a second requirement is that I can't predict their every reaction before they have them. Think of how someone might react if his or her significant other ends the relationship. There are many, many truthful ways—ways that would seem like a human being reacting and not like a space alien behaving in some bizarre, unbelievable way. An actor's job is to know the breadth of human possibility and the depths of his or her own possibilities. He or she must pull from this well and surprise us. Otherwise, the actor becomes boring and predictable.
There are many ways and actor can surprise. Gary Oldman and Johnny Depp surprise us by being truthful while playing multiple, very different roles. Jack Nicholson surprises by being ... surprising. Even though he's not a chameleon like Oldman or Depp, you never know what he's going to do next. But whatever he does, it's grounded in psychological reality. It never seems fake. Christopher Walken, Glenn Close, Al Pancino, and many others have a surprising danger in them. They're a little scary to be around, because you feel they might jump you or blow up at you at any time. They are ticking time bombs. And, of course, many comedic actors (e.g., Julia Louis-Dreyfus) surprise us in all sorts of quirky, zany ways. Or watch Katharine Hepburn and Cary Grant in Bringing Up Baby—absolutely surprising and absolutely truthful. Another great example of surprising acting that never seems fake is Diane Keaton's work in Annie Hall.*
Third, the actor is vulnerable. Great actors share the parts of themselves that most people keep hidden. They are always naked. (Some are literally naked, but I'm talking about emotional nakedness.) Bad actors are guarded. They don't want to share the parts of themselves that are ugly, mean, petty, jealous, etc.
There are so many examples of actors being naked onstage and screen. My favorite is Rosalind Russell in the movie Picnic. She plays a middle-aged teacher who is in danger of growing old and dying alone. There's a heartbreaking scene in which she begs a man to marry her. She goes down on her knees in front of him. She gives up every scrap of dignity inside her and lets the scared, hurting parts of herself burst out. These are the same scared, hurt parts that are inside all of us—the parts we work hard to hide.
This ties in with everything I wrote above: When actors are exposed and raw, it's always surprising. And if it doesn't seem real, there's no point in it. In fact, this sort of emotional nakedness is very hard to fake. If you ever get a sense that an actor is showing you a secret part of himself, he probably is. Examples are Julianne Moore, Bryan Cranston, and Michael Redgrave in The Browning Version. He turns himself inside out and wrings out all his pain.
Fourth, the actor knows how to listen. It's fascinating to watch actors when they're not speaking. Some are too caught up in ego or technicalities (e.g., trying to remember the next line) to totally focus on whomever it is they're acting with. Others seem to register everything they hear. You can see whatever is being said to them physically affecting them, as if the words are slapping them across the face. Watch Claire Danes. She's an amazing listener.
Fifth, the actor has a well-honed “instrument,” by which I mean he knows how to use his voice and body to serve whatever role he's playing. This doesn't necessarily mean he's slim and has a six-pack; James Gandolfini used his body well. It means he knows how to move and talk in expressive ways. His voice and body aren't fighting him or holding tension that's inappropriate to his role.
One negative example: Kristen Stewart. It's almost painful to watch her. She looks like she'd rather be anywhere else besides in front of a camera. She is (or seems) very self-conscious.
To me, Hoffman was great because he embodied all of these traits. He was vocally and physically gifted. He wasn't in great shape, but he used the shape he had in expressive ways. If you watch him closely when he's not speaking, you'll see he always listened to his co-stars closely. What they say affected him deeply, and his reactions grew organically out of whatever they had previously said or done to him. He was profoundly vulnerable. Always. This was his most distinctive trait. You always knew what you were getting from him was raw and honest. It was this rawness—as well as intelligence and a sly sense of humor—that made his work surprising and fresh. And I never once saw anything from him that seemed fake.
I don't hate Tom Cruise the way some people do. To me, he's believable most of the time. He's just not very interesting. He rarely surprises me, and he doesn't seem to dig deep into a anything raw or vulnerable inside him. He seems guarded. The must vulnerable I've seen him is in Eyes Wide Shut, in which he did some good work. But it wasn't brilliant, and it's not his norm.
Keep in mind that many people (who aren't themselves actors, directors, or obsessive film buffs) aren't very clear on what an actor contributes to a film. It's not necessary for most audiences members to understand who does what during production. Lots of people think an actor is great if they like his or her character. But that's often a function of good writing more that good acting. Or they think she's good if she pulls off some impressive effect, such as gaining or losing a lot of weight or pretending to be handicapped. Those are impressive stunts, but they aren't the core of what actors do. If you forced me to rank Dustin Hoffman in Rain Man versus Dustin Hoffman in Kramer vs. Kramer, I'd say he did more exciting work in the latter. In Rain Man he was able to hide behind some stunts. In Kramer vs. Kramer, he just had to be truthful.
Some people think acting is good if they like the movie. Keanu Reeves, in my mind, is a horrible actor—mostly because he's wooden and fake. It often seems as if he's reading from cue cards rather than saying words that are his. There is a difference between playing an undemonstrative person and being a wooden actor. In fact, playing someone who is reserved is very difficult (because you have to act without showing very much), and the actors who pull it off are brilliant. I would point you to Anthony Hopkins in Remains of the Day, Tommy Lee Jones in many of his roles, and even Clint Eastwood in Dirty Harry. These actors manage to convey the sense that although they have stony exteriors there's much going on underneath.
To me, Reeves conveys an actor who is showing up and saying his lines. Having auditioned many actors, I'm used to hearing ones that can take any writer's lines and make it sound like their own words. And I'm also used to less experienced (or less gifted) ones who sound uncomfortable with words that aren't their own. They sounds as if they're are reciting or reading something. They sounds scripted. Listen to Reeves in this clip, especially at around 10 seconds in, when he says, “I have offended you with my ignorance, Count.” Many of his line-readings sound like that to me: He has not fully lifted them off the page and into his own mind and body. I don't believe much else is going on underneath except maybe nervousness. I don't know if you can see a difference between Reeves, above, and Tommy Lee Jones here. They are both pretty deadpan. The difference, for me, is that Jones seems to be speaking his own words, even though they are just as scripted as the ones Reeves speaks. Jones is just much more comfortable in his skin and much more able to “own” his lines. If you feel otherwise, that's fine. Remember, it's subjective.
But some people like Reeves because they think the Matrix films are cool. They confuse the movies with the actor. If some other actor had been in those films, those same people would have liked him, but since he plays the protagonist, they focus on him.
Finally, many people confuse an actor's life with his work. Tom Cruise is a good example. He's a high-profile scientologist, and many people dislike that religion. They dislike his acting at least in part because they find him unsavory as a person. To some extent, this may be a sign of bad acting on his part. At least, he's not a good enough actor to make people forget about his private life while they're watching him in movies. To some extent, it wouldn't matter how skilled he was. Currently, many people are having strong reactions to work by Woody Allen and Mia Farrow that have nothing to do with what they're doing on screen. I'm not even remotely saying such people are wrong, stupid, or crazy. I'm just saying that people's reactions to actors are often complicated and not 100 percent influenced by their performances.
*Correction, Sept. 10, 2014: This post originally misspelled Katharine Hepburn's first name.
Also in Slate:
More questions on Quora: