The "Brain in a Vat" Paradox

I am a philosophical skeptic. I hold that nothing can be known with absolute certainty. No belief can be known as an absolute truth. The "brain in a vat" is a thought experiment that serves as an example. 

Suppose that we might remove a living brain from a body and suspend in a container filled with some kind of life-sustaining liquid. To the neurons in the brain we attach wires which are in turn connected to a computer that can provide sensory signals identical to those received when the brain is in a living body. 

The brain in the "vat" would be unable to distinguish whether the sensory signals it receive and on which it acts is from a living person or the computer. The brain would PERCEIVE reality to be the same in both cases even thought the reality was entirely different in each case. The computer sent the signals corresponding to a person walking when, in fact, no person was walking. 

Today Brain-Computer Interfaces (BCI) are a reality but  function in reverse from the "brain in a vat". Neural activity associated with thought are fed into computers which control mechanical devices to perform the actions envisioned in the thought process. The action imagined in the brain becomes a reality in the world. This technology is already being used with various limbs and digit prosthesis.

But, then again, is it all but an illusion?