As you doubtless noticed, Harvey Dent "makes his own luck" through use of a rare two-headed coin. The explosion that turns him into Two-Face scars one side of it, turning it from an easy way to win bar bets to something infinitely more interesting. Comic book fans have known about the coin since Hector was a pup, but few others realized its significance as a symbol until Aaron Eckhart started using it to score dates and decide who lives or dies. (We're not talking about Tommy Lee Jones here. Nope. Uh-uh.)

On the surface the symbolism is pretty obvious. Dent flips the coin to decide any questions that need answering, leaving his actions up to fate rather than making any conscious choice himself. It's an easy short-hand way to reflect what's going on in his mind, both before and after he goes nuts.

As Harvey Dent, it shows us his propensity to job the system. Only he knows that it has two heads, after all, which lets him trick people into making bets that he knows he's going to win. Early on, he mentions a fairly benign use for it—getting him a date with Rachel—but later on it gets dark. Really dark. As in "scaring a criminal psychotic into believing that Dent means to kill him" dark.

He's cheating, of course: setting up rules that he has no intention of following in order to get the results he wants. But he believes he's doing it all for the greater good, and let's face it, he probably is. The giggling sociopath he puts the hurt on with it knew important things and unless the good guys found out what they were, more people were going to die. So Dent used the coin to cheat, and we might have done the same in his circumstances.

But at the same time, he's kind of making the Joker's point. There are no rules in this world, except the ones that people make up. And when they don't like them, they change them or find loopholes around them, which basically renders them meaningless. That make a lie out of the very system that Dent has sworn to protect: the mild, forgivable hypocrisy that most of us accept as necessary in a flawed world, but which the Joker believes makes each of us a potential monster. All of that wrapped up in one little coin carried by the embodiment of the system the clown wants to blow up.

And blow it up he does. Once Dent gets his impromptu facial, the coin follows suit. Its extra head becomes scarred, erasing the façade of fairness that it once carried and becoming a unique reflection of the old head-tails coin we all know and love. The façade has dropped, only now at least half of it is dark and ugly and scary. Kind of like Two-Face himself, who (with a little prodding from the Joker) has rejected the compromises of the system in favor of rubber room insanity.

Now, every choice is decided by the coin, telling him who to kill, who to betray and who to blame for everything that's gone wrong. There's no room in his life for extenuating circumstances or exceptions to the rules. It's harsh and unyielding, but it's not hypocritical… and to the Joker that's all that matters.

Here's the thing though: the scarred coin, like Two-Face, is now broken and ugly. It doesn't promise anything but a messy death and no human thought or morality goes into its decision making. Sure it's not deceptive or hypocritical, but in exchange for those nebulous principles, we get a former DA gunning down cops, terrorizing small children and threatening to undo all of the good things that Dent, Gordon and the Batman have been up to. All in the name of ideological consistency.

That lack of flexibility—Two-Face's freshly minted inability to exercise prudent judgment and reasonable discretion—proves far more damaging than any occasional bent rules. The scarred coin is honest, but it's also ugly and sinister. The original coin may have been deceptive, but it was also elegant and beautiful: something worth admiring.

And just as the coin reflects Harvey's increasingly tenuous state of mind, it also demonstrates why the Joker's way isn't rational.

Sometimes we need to bend the rules. Sometimes we need to exercise a little common sense and step in when it's appropriate to do so. "You know the thing about chaos?" the Joker says. "It's fair." He's wrong. It's not fair; it's arbitrary, like the coin. And neither he nor Harvey have the clarity of mind to figure that out, even when it's staring at them in the face.

That's a lot of meaning for one little minting mistake to handle, but if you know the character you can see how inseparable he is from his coin: a reminder of what happens when you take things just a little too seriously.