Brain in a Vat

Philosopher Descartes makes a bold proposition that the external incidents and internal thoughts we think are self-experienced is instead the result of manipulations by an all powerful evil demon. We are being deceived to think and act a certain way. What we believe, see, hear or feel are controlled by fate-- something bound to happen or sense because we are merely brains hooked on to a life-support machine. Our brains are fed with external memories, and ideas we never experience, are yet ours. "Life" would seem normal and reality-like, but everything that has happened or will occur is an illusionary happening. It is as if we are living in a seemingly reality-driven fantasy; however none of the things that transpire or occur is actually real.

What is described above obviously appears impractical and complicated. Before debating the validity of the brain in a vat hypothesis, we have to first distinguish between what are beliefs and knowledge and in addition comparing the truth and falsehood among them. In other words, what makes a belief and knowledge true or false? A belief is one's interpretation towards a proposition or simply personal perception. With regards to the beliefs you make, the validity and falsehood of that belief is flexible because your attitude governs whether it be true or false. However, the justification of the true or false beliefs is much complex. Justification needs evidence and reasoning. Possible examples of types of justified belief:

For the former, justified true belief is as followed:

One, O knows that a proposition P is true...

1. P is true

2. O believes that P is true

3. O is justified in believing that P is true

Thus, the following is considered to be part of the definition of knowledge; however it is not sufficient enough to be definitive of knowledge. Knowledge is based on interpreted, unbiased and objective facts and not merely considering the thinking subject.

For the latter, the justified false belief is as followed:

One, O knows that a proposition P is false...

1. P is false

2. O believes that P is false

3. O is justified in believing that P is false

The following is an example of a justified false belief, since the proposition is held false. The false belief is justified because conclusively the premises are all true and sway significance with reasoning.

Most knowledge tends to derive from our senses. For instance, the knowledge that ice is cold comes from our senses. If you place your hand on an ice cube, you feel a cold sensation. Thus, the idea of being a brain in a vat has never occurred upon our senses. But we still cannot be conclusive as to say that we know (however, we can say we do not believe) we are not brains in