Here's the proof (what's in bold is the summary):

1)

**Our consciousness is caused by a series of computations.**

The proof revolves around the idea of Information processing theory of consciousness which says our brain is like a computer and that our experience of consciousness and qualia is the result of information processing.

2)

**Any computations within our brains can be represented elsewhere in an infinite number (or at least an extremely high finite number) of ways.**

Within a second of time let's say our brain performs 10^15 calculations per second. For the sake of simplicity, let's say a second of consciousness is represented by processing involved in solving a problem like 78+14. Then going through the motions (4+8 is 2, carry the 1, 7+1+1 is 9, answer is 92) is equivalent to a second of someone's consciousness experience of eating a cake. Elsewhere in the universe there may be a computations going on like 98+34 and 73+19. The processes for solving these two equations is the same processes for the 78+14 equation. The 4+8 from "98+34" and 7+1+1 that would come from the third operation in doing "73+19". So the same information processing used to solve 78+14 can be found in other places.

Since other data can be interpreted to represent any arbitrary information processing then there should exist virtually inexhaustible ways to interpret data to represent what ever information processes going on in our brain at any given moment.

3)

**Since the information processed by our brain at any given moment can be represented elsewhere in an infinite number of ways, each of those consciousnesses would feel indistinguishable from our own.**

4)

**The probability of my consciousness existing within my actual brain given each copy of me will feel like the me is 1/(total possible places copies of my consciousness exists). Which is essentially 0.**

5)

**Therefore the consciousness I am experiencing at any given moment is most likely not the one being caused by my brain**

Then this got me thinking more like other possible brain states that would exist of events that did not happen. For example, if I played the lottery and won there would exist a brainstate of my experience of winning the lottery. And also an infinite number of copies of this brainstate can be represented elsewhere. But that information would still exist without needing the event to actually happen. In essence all things that can happen would exist in our universe somewhere. It's kind of like the multiverse theory except instead it's all different realities in our own universe.