Internal Story Arcs

If you look into writing advice, whether in a video or in a book or on a website, you will find a lot of mentions of the ‘internal arc’ for your main character (it’s also often referred to as ‘character arc’). It’s a necessity, don’t you know? Yet, what is that elusive ‘internal arc?’ And is it really so necessary?

Let’s look at the second question first. Is an internal arc always necessary?
Well, no. Some types of stories don’t really need such an arc. In pulp stories, superhero comics, or comedic series, there usually isn’t a lasting change to the recurring characters and especially not to the main character or characters.
While in some stories characters might gain new skills, they usually are not asked to overcome a flaw (which is what an internal arc is usually all about). They are good at what they do already, they don’t really need to improve. This goes both for pulp heroes and for comic book heroes.
Similarly, many series, especially those of a more comedic bent, rely heavily on resetting the situation again between episodes, which means that no development of a character will be lasting. There might be changes in relationships (such as marriages or breakups) which last, but the characters usually don’t grow out of flaws — especially as flaws are usually chosen to allow for comedy to happen.
All of these stories need an external arc — something must be happening and the main character or characters must be involved in it. Stories without an external arc are highly experimental and usually don’t find a lot of fans. Stories without an internal arc might be looked down upon by the ‘high literature’ crowd, but they can still be very successful. So, no, depending on what you write, you might not need an internal arc at all.

If you want or need an internal arc, though, what is it about?
Internal or character arcs are almost always about a main character (rarely a supporting one) overcoming a ‘character flaw.’ ‘Flaws’ in this context are normally negative personality traits, more rarely negative habits. Characters are flawed for being shy, aggressive, arrogant, selfish, etc. They need to overcome that trait not only for their own betterment, but also in order to gain something they will need in the climax of the story — often reinforcements, sometimes information or a specific object.
It’s important not to overdo the flaw in the first place. A character who flies off the handle quickly should not beat people within an inch of their lives. They might bruise someone or cause damage to furniture etc. instead. While that is still bad enough, it is not something the audience will find unforgiving in the main character. During the story, the character then has to understand what their flaw is and has to let go of it. That can be through being told about it or through bad consequences. In the end, overcoming the flaw should pay off in some way during the climax.
For example, Han Solo’s flaw in “A New Hope” is his selfishness — he only helps for money (hence Luke’s ‘she’s rich’ line to get Han to help him rescue Leia). When he comes back in the end and saves Luke from Darth Vader, he is overcoming that selfishness and is putting his friends before his own safety (as he’s not paying off his debt to Jabba which will come back to bite him later).

One thing you should keep in mind when you’re choosing your internal arc, though, is that it should always connect with the main external one. For instance, if your internal arc is focused on your main character overcoming their shyness, then the climax of the story might include something like speaking in front of a large crowd (where shyness is definitely a problem), not defeating an enemy in combat while nobody else is present (you can be shy and a masterful fighter at the same time).
The main external arc will always be the more important one in any story, every other arc has to feed into it at some point in some way. Overcoming a flaw can help the main character overcoming a roadblock, it can give them an ally they haven’t had before, or it can gain them an object or information they need to win in the end. So if your main character’s internal arc doesn’t help with the external one in any way, it could be considered superfluous.

Internal arcs are an excellent way to give more depth to the story and add another reason for tension as well. By connecting overcoming a flaw to the things a main character needs to do in order to win the day, there is another area where problems can and most certainly will occur.
It also depends a lot on what kind of story you’re writing whether or not an internal arc can enrich the story. In an adventure story, most of the threats which can push tension are external — henchmen who come for your main character, collapsing bridges, or statues coming to life, for instance. In a romance story, on the other hand, it can matter a lot whether or not your main character can overcome their shyness or the love interest can grow out of their arrogant behaviour.
The more a story is focused on the people in it, the more useful and important can an internal arc be. The more a story is focused on action, the less useful and important an internal arc will normally be. That doesn’t mean that an action story can’t have an internal arc and that a romance story with a purely external arc can never work, but generally you will pay more attention to people’s internal struggles when their emotions matter for the story as well.

So to put it all together: an internal arc is not quite as important as an external arc for a story, but a lot of stories profit from having an internal arc or character arc at least for the main character. An internal arc should support the main external arc of the story, as this one will always be the more important one. Do not overdo the character flaw for your main character — despite being flawed, they must still be likeable or at least act in an acceptable manner. If an internal arc can add additional depth and tension to a story, you should have it in there, if not, you can just as well do without it and invest more energy into the external arcs.