We all have our tastes, our preferences, our prejudices. (I know I do.)

And one thing I’ve figured out: sometimes I have a preference (or, if you prefer, a prejudice) that has a clear reason for being — a motivation, if you will — but I haven’t figured out what this reason is. (This leads to those “I really hate romances set on Greek Islands but I have no idea why” moments.) (You might also think it leads to those “I can’t understand why you enjoy sugar in your tea” moments, but that’s quite a different thing. I need no subtle motivation to know that sugar in tea is just a sad, sad thing.)

Why is this on my mind? Because I’ve just reasoned out the reason for one of my prejudices preferences.

And this makes me happy. Any sign that even the smallest part of my brain (or, indeed, any part of the world) is organized by something approaching logic makes me feel warm and snug and smug.

Now, I have mentioned that one might prefer to call this preference of mine a prejudice, right??? And I have made it clear that this is just my taste, my bias, one of my likes and dislikes??? (And I do have lots and lots of dislikes, particularly concerning vegetables and blue eye shadow.)

Because I honestly mean no criticism of anyone’s books (even books I may have read). After all, my refusal to eat cauliflower in no way implies that I dislike, disparage, or disrespect the cauliflower on your plate! And I particularly don’t disapprove of you for eating it (or reading or writing it.)

So…here it is.

I realized quite a while ago that I get surprisingly annoyed at reading historicals in which there exists perfect birth control… You know, the book where the virgin aristocratic heiress has a naughty aunt who teaches her (or provides her with) a fool-proof way to fool around with some hunky fool for as many months as she wants, with zero chance of pregnancy.

Now, it’s not like I always insist on perfect historical authenticity or total realism…after all, I’m a big fan of Shakespeare and Georgette Heyer. (Yes, I know that when Viola and Rosalind and Leonie dressed up as men they would still have looked like girls…but I just don’t care!)

So…why this great irritation on my part? Why does the better-than-the-year-2008 contraception in 1808 in just get under my skin? Well, I finally figured it out.

The way I see it, a huge amount of the psychology, sociology, laws, economics, and fashion involving middle and upper-class women in 1808 Britain was based on the fact that reliable contraception did not exist.

After all, think how much the invention of the pill affected social norms and behavior involving everything from cohabitation to premarital sex to middle-class wives working outside the home to romance novels to adoption.

So, for me, reading a historical with foolproof contraception is as bizarre as reading some of the science fiction written in the 1950’s — the kind where the fifty-year-old workaholic hero’s wife has all her housework, shopping and entertaining done by robots, but she still doesn’t have a job or even a hobby. (I’m sorry, but what does she do all day???)

So there you have it. When it comes to reading about perfect contraception in 1808 (or mindless housewives in 2828)…I simply would prefer not to.

Cara King, who once wrote an essay arguing Bartleby the Scrivener was a ghost