There are a lot of ways to make characters and one method is blank slate. A blank slate character is exactly what it sounds like: a blank slate. They don’t really have a personality or character at all. They have a few traits or maybe a quirk but they aren’t their own person. They don’t make any decisions that aren’t absolutely necessary. Oftentimes, things happen around them rather than them deciding to make something happen.
In college it was extremely frowned upon to use them because it’s considered lazy and you’re not creating a character at all. You’re supposed to make a believable person. Your reader should think they can reach out and touch the person, that’s how real you’re going for. I suppose the thought is (though no professor came right out with it) that you want your reader to be along for the ride. You want them to feel like they’re going on this adventure with a group of their own close friends. You want characters they can relate to and feel close to and draw similarities between themself and these characters.
Now, I think that blank slate characters get a lot of unnecessary hate. They aren’t the best choice for a story. If you want to be literary and write very good fiction then you should avoid them. But I can’t really say they’re never useful because there are plenty of very popular books that use them.
I’ll be using Twilight as an example in this post because it’s an easy one. Bella Swan is a blank slate. She is, by herself, boring. Sorry, if you like Twilight that’s fine, I’m not insulting it, just looking at the use of it’s main blank slate character. Bella does not make choices or decisions that matter. The entire love-triangle is a convoluted mess because she chooses, in the first book, Edward. But it’s not even as though she really chooses him at all. He is the obvious, and easy, “choice”. The narrative makes it very clear that he is the only option for her.
So Bella doesn’t make decisions. Things happen around her and to her but never because of her. In writing, this is referred to as her level of agency. How much power does she exert over her surroundings? A character built into a character has a lot of agency. They make choices that affect those around them. They build relationships, they change other people, they make choices that have an effect on the overall story. In essence, they make the story happen. Without them, without exactly who they are as a person, the story wouldn’t work at all. There would be no story.
For a blank slate, they could be pulled out of the tale or replaced with anyone and the story would still work because they are not actually necessary. Bella (as far as the first book is concerned) could be easily replaced by anyone. And that’s the POINT.
Frowned upon in school, sure, but the point of a blank slate is not to make a character. It’s to make a part for the audience. How many girls read Twilight and said “Oh, I could be Bella! We’re so alike!”? Because Bella doesn’t have any agency or character so anyone can put themselves in her place and say “I would do the same thing.” Not because they would, but because the narrative around them forces them into a decision and makes it as easy as possible for them to make that choice. For a blank slate, the pros of a decision can so far outweigh the cons that there’s no reason to even consider the other option. They will, of course, take time to consider it anyway, because the narrative needs to show the illusion of choice on the part of the character.
If you want to write the audience into your story, without going crazy and trying second person, then write a blank slate character. I don’t think there’s anything particularly wrong with using them. No one who understands how to write is gonna call your work high literature (unless you go back in time when blank slate was fairly standard) or consider you a great author. But hey, if you want to use them as a literary device then more power to you. It seems to have worked quite well for Stephanie Meyer at any rate.