You would likely have a sense of disembodiment. Even though the brain is "the organ of thought," it relies on bodily feedback to have a sense of where it is in space. You would need a pretty sophisticated vat to not only mimic the seven trillion nerves in your body but also their interaction with each other, your brain, and the physical world. Anyone capable of pulling that off could do away with a physical brain altogether and simulate the whole thing.
Also confront creationist ILLOGIC by asking them why their alleged gawd created a fossil record that is undeniably billions of years old which the bible claims was all invented 8000 years ago ???? Our memories of cave paintings 40 thousand years ago AGAIN INVENTED INTO OUR BRAINS for future debates 8000 thousand years ago ....so what I just typed could have been invented by a creationist prayer ANSWER from their bible gawd geebush geehobah ghostholes an hour ago and I have zero free will their gawd made me a programned Atheist robot straw man for Sunday School believers
Your brain IS in a jar. It's called a skull. And what you remember as your entire life, and your current experience are made entirely inside that brain. You get assorted nerve impulses from your nervous system and that is all there is. So, where is the significant difference?
It is what it is, and there's no way to tell unless you find a trick.
I've always had lucid dreams, hard to tell if I'm dreaming or not, but if I'm dreaming and try to read a book all I can see is symbols, nothing making sense, so I know I'm dreaming.
Which scared me no end driving all night through Kansas, their road signs are so badly maintained they're all but illegible, so I kept pulling over afraid I'd fallen asleep.
It might be. The alternative is that your brain is sitting in a "jar" made out of human flesh. Either way, your brain experiences the world through external sensory input and you can never be certain any of it is an accurate representation of reality. Sweet dreams.