Conspiracy theory is a term that originally was a neutral descriptor for any conspiracy claim. However, it has come almost exclusively to refer to any fringe theory which explains a historical or current event as the result of a secret plot by conspirators of almost superhuman power and cunning. (с) Wikipedia.
In 1989 when Bob Lazar claimed that he had worked on military base, and he was contracted to work on alien spacecraft. It was the begining of the most famous conspiracy theories - "Area 51". It was mass media sensation. A lot of thoughts were added, like there was teleportaton researches, time travel, weather control and other products of reporters` imagination. However, too high security of this base and unwillingness of US goverment to speak about it creates a lot of conspiracy theories.
There is a conspiracy theory about swine flu - the virus was created by goverment to reduce people population on earth.
As we can see this theories are unproved and we can`t believe them. We can look deeper and realise the real "incredible truth" - our planet ruled by aliens! "X-files" and "Men in black" just made for us to unveil the truth. Some rebels from ZOG, alien organisation that rules our goverments, telling us the real situation on our planet! If we look more narrowly to global political events we can see that something argues us with one another, we can see lots of viruses that causes epidemies that reduce our population. Aliens are waiting us to loose our power and then they will strike.
"Brain in the vat" theory is an argument for Solipsism. Solipsism - theory that we stuck in our mind. We can`t go beyond our sense impressions, we can`t share our ideas with others, just express them in our words. Language can be doubt with solipsism as well. As example idea of "fork" for me can be different from other people ideas.
"Brain in the vat" theory can be interpret like " some evil scientist put your brain in the vat, connected it to the supercomputer and my brain recieve the same impulses, like in body", like virtual reality.
Before invention of computer famous philosopher Decartes said that "it might be an evil demon, contrilling my experience".
Also Decartes decieded that he can doubt everything except one thing, that we can think. This is also an argument that we are. "I think therefore I am" Descartes said.
The puzzle problem is a phylosophical problem. There is a question: "If we will die and then some scientists wil duplicate your bodie atom-to-atom. Will it be you?" In my opinoin it is a qestion of your belief. If you believe in immaterial substance, the soul, then you will find this idea horrible! But if you like John Locke, famous empiricist, and you believe just your sense impressions and eperience then you will agree, that it make sense. I`m not supporting empiricists point of view, but i don`t believe in "soul". I think it is just a way to idealize a human being. We are just a flesh.