I've heard this term being used before though I don't exactly comprehend its full meaning, and whenever I've tried looking on the internet it leads me to articles in which it's being used rather than giving me explanations. There's a point in my story where I think I want to use it but I have a feeling that I'm mistaking "vacuum" wrongly in this situation.
Usually it means trying to assess something without having the proper context. Often this might be used with respect to a piece of writing or a moral dilemma.
I see, so I did mistake the use of vacuum. At first I thought of like a vacuum cleaner and the phrase was another way of saying stereotype, like if I met a person from New York and they were rude, I would automatically assume they possessed all those other stereotypes. I had a feeling the term vacuum here was being used to mean "nothing". Thanks!
that is what it means... as in you are making judgments with nothing to go on... no background/experience/knowledge of the subject/person you are passing judgment on...
A vacuum is a space which contains nothing. It has come to mean an airless space, but the original neaning is just emptiness. Judging in a vacuum therefore means coming to a decision with nothing to base it upon.