09 September 2005

Similarity Versus Identity

It's a cliche: your driver's license picture doesn't look like you. But if this is really true, then what is the picture for?

The stated intent is that the picture is supposed to prevent someone else from using your driver's license. Everyone in the U.S. who's under 21 and enjoying a beer right now knows how effective the picture is for that purpose.

The driver's license picture fails as a descriptive reference because people basically all look the same, and because people don't look very carefully either at pictures or at other people.

Recognition without similarity

Don't believe it? Who's this guy?

You recognize Jesus instantly, even though he didn't actually look like that. In fact, you recognize him no matter what he looks like. He can have brown hair and brown eyes.

He can have black hair and dark eyes.

Or he can have blond hair and blue eyes (if you want a really disturbing experience, by the way, go to Google images and search on blond jesus - no quotation marks).

Part of this, of course, is context. If you run across somebody wearing a crown of thorns and sporting a halo, Jesus is going to be on your list of possibles, and you may not look too closely at the height, weight, eye color, hair color, or restrictions fields of his license.

Similarity without recognition

Context is a reasonable guide to recognizing pictures of Jesus, because nobody really knows what he looked like - there aren't any contemporary pictures or descriptions which survive, as far as we know.

But even without context, we would all recognize pictures of Jesus, because the Christian community has for centuries been in the habit of using pictures as descriptive references to endow him with certain physical features - tall, thin, long face, beard, benign expression, etc....

Here's another test: do you recognize this guy?

You probably don't, but Jesus would have; when he held up the coin and asked "whose face is on this?", he was looking at this picture - it's Caesar Augustus, and you can bet your last denarius that it's a very good likeness (what do you think happened to sculptors who made Caesar's nose look too big?).

Mistaken Identity

We all have both these problems all the time, even with people we know well. How often have you been at a party, recognized a friend across the room, called out his name, and then realized that the guy across the room is somebody else entirely, and your friend isn't even at the party? That's recognition without similarity.

On the other hand, how many times have you answered the phone and conducted a conversation for several minutes before you finally had to break down and ask "I'm sorry, who is this?" (and then had to say "Oh, mom... you sound different - do you have a cold?") That's similarity without recognition.

Cases like this sometimes make the news. Recognition without similarity doesn't have to be based on a picture of your face; a picture of your finger (for example) will do. If you're Brandon Mayfield, a picture of your finger might look something like this:

Somebody who saw a different picture of a fingerprint - maybe the one below - might decide that it looks like a picture of your fingerprint...

...and if that somebody were the FBI, they might arrest you if the second fingerprint picture was taken at the scene of the Madrid train bombings. You might be more likely to be arrested if the context (for example, the fact that you are a Muslim) reinforced the impression of similarity created by comparing the two fingerprints.

This really happened; these aren't the real fingerprints, but the real second fingerprint was an image of Ouhnane Daoud's finger, and Brandon Mayfield was released.

The point, of course, is that because identity is subjective and identity changes over time, identification is necessarily a process of judging the degree of similarity of two descriptions (or images), and the result of identification is a probability rather than a certainty that the two descriptions refer to the same person or thing.

Art and Ambiguity

The ambiguity of identity creates rich possibilities not only for drama (The Man in The Iron Mask), for comedy (Twelfth Night), and for crime (The Sting), but also for art.

My favorite example of art and the ambiguity of identity is the work of J.S.G. Boggs, who creates drawings of banknotes, which he then "spends" by exchanging them for goods and services. He always makes it clear to people that he's giving them artwork, not "real" currency (whatever that means!), but he also always requires change and a receipt.

Several legal cases on several continents have centered around the question "is this a counterfeit banknote, or is it something else?" So far, the answer has always been "it's something else." You can read about Boggs here.

07 September 2005

Identification And Modes Of Reference

What if I know an individual and you don't? I can tell you all the stories I want, but the stories won't be useful to you until you have someone to associate them with. To make the stories useful, I have to IDENTIFY the person to you. I can do this in two ways.

If you and I and the individual in question are all in the same room, I can point to the individual and say "See that guy?" The act of pointing to a person or thing to refer to it is called


It's called "indexical" because (in the English-speaking world anyway) you use your "index" finger to point to people. Pointing at something is a way to connect a reference to a thing (a name, for example) or a story about a thing (an identity, for example) to the thing itself. Indexical reference only works if you and I can both see the thing I'm trying to point to at the same time. Links on the web are a form of indexical reference, and they break when something moves out of view. Weirder things than broken links can happen when indexical reference breaks on the internet - things like this, for example. Once I've referred to a person using indexical reference, I can start telling stories about that person, in order to communicate my view of the person's identity to you. I can say, for example, "That's Kim Cameron; he's the guy who wrote the Laws of Identity. He works for Microsoft, because they bought Zoomit, which he founded. He's a frequent speaker at the Burton Group Catalyst Conference, and ...." I could go on and on here, but you get the idea. If you and I can't both see the person or thing I want to identify to you, I can't use indexical reference. Fortunately, I've got another option.


Let's imagine I want to identify Kim to you, and I can't point to him. Maybe you can't see me pointing because I'm typing something about Kim into a blog and you're reading the blog in a Starbuck's coffee shop thousands of miles away.

Since I can't point, I have to do something else. What I do is this:

"Look for a guy with curly, white hair, a grayish walrus moustache, taller than me and a bit heavier, dressed business casual. He has a softish Canadian accent, wears glasses, and smokes." If I give you this description and you run into the guy in this picture, you might be confident to go up and introduce yourself: On the other hand, you might not be confident enough to go up and introduce yourself, because, after all, my description isn't terribly specific, and it probably applies equally well to thousands of people; I'll talk about this some more in the next blog entry. The fact that descriptions are all ambiguous to some extent is one reason why even people as well known as Kim wear name badges at conferences (the other reason is that the conference organizers want to make sure that even people as well known as Kim pay their conference fees).

Kim's name badge brings us to the third mode of reference; once you and I both know an individual (so that we've gotten past the need to identify the individual), we can refer to the individual using a name.


This mode of reference is called NOMINATIVE REFERENCE. It's not foolproof. I'm a great example.

My name is "Bob Blakley", in the sense that this is what everyone who knows me actually calls me.

In another sense, though, my name is "George Robert Blakley III", because that's what appears on my birth certificate and various other official documents.

In a third sense, my name is "Bob Blakely", because lots of people misspell my last name (go ahead, Google it - you know you want to! About half of the top hits in a search for "Bob Blakely" are actually references to me - including the first listing, which is there because Kim Cameron misspelled my name when constructing a technorati link to me from his recent post; the misspelling has since been corrected but its progeny live on in the Google cache).

These things happen because, generally speaking, there is not a one-to-one correspondence between people and names. Many people have nicknames, assumed names, stage names, married names and maiden names, aliases, pen names, and so on. The government hates this and is trying to make it harder and harder to have multiple names - I've had to change the name on my frequent-flyer cards from "Bob" to "George Robert" in order to get on airplanes, for example - but the effort to eliminate alternate names is going to fail, if only because no one is actually going to call Camilla's husband "Charles Philip Arthur George Windsor, His Royal Highness The Prince of Wales, Duke of Cornwall, Duke of Rothesay, Earl of Carrick, Baron Renfrew, Lord of the Isles and Great Steward of Scotland, Knight of the Garter", because that would just be a pain in the ass.

But let's go back to the first sense - try a Google search for "Bob Blakley". It turns up the usual ten billion references to me. But it also produces another interesting thing - a bunch of links like this one. These are links to my father. He's George Robert Blakley, Jr., also usually known as Bob, also a computer security researcher, also from Austin, TX, and so on. And if you look far enough down in the list (apparently I'm very famous compared to many other Bob Blakleys) you'll find entries like this, which point to people to whom I'm not related (as far as I know).

This happens, of course, because in general there isn't a one-to-one correspondence between names and people. In fact, it's a dead cert that lots of other people have the same name as you, unless your name happens to be ... which is also a pain in the ass.