You don’t know whether or not you have hands.
Brains in Vats, or BIVs, are floating brains sitting in , well, vats. That’s a metaphor really for a disembodied mind; a BIV hypothesis isn’t meant to be taken literally, it’s just a modern rendition of mind/body dualism
So, suppose you are a BIV and imagine that evil scientists are feeding electrical impulses into your brain to create the environment you are in now. This illusion, is so complete, that it is an aloe world (sp?), a virtual world which you experience with all 5 senses and is virtually indistinguishable from reality
Well, if that were the case, then you would be experiencing just what you are experiencing now. Not to mention you’d still be here, reading this
One thing you should know about BIVs, is that they don’t have hands
But something you DON’T know, is that you’re NOT a BIV
Therefore, you don’t KNOW, whether or not you have hands.
Try to figure that one out.
Though, for myself, personally, I think it makes the evil scientist look rather sad; to think they’re actually laughing over something as trivial as a BIV not knowing whether or not it has hands.