First I would like to address the idea of knowledge in view of a philosopher. A philosopher would think of knowledge as a three point understanding of something:
1. That the idea is true
2. That the idea is justified
3. That the idea is believed
So knowledge could be said to be a true, justified belief.
That said, let us look for knowledge in deciphering déjà vu and precognition.
Déjà vu is a french phrase, déjà meaning already and vu meaning seen. So Déjà vu means already seen. When someone experiences this strange phenomenon, it is the feeling that they have already seen whatever is happening before. The strange feeling when you ask, "has that happened before?" Déjà vu is often attributed to a dream, though sometimes people are entirely convinced that the happening has actually already happened.
However, some people experience something during, or after, déjà vu when they can actually predict what is going to happen next. Someone knows that a cup will fall, then the cup falls. This, I would argue, is not a part of déjà vu, but rather an actual glimpse into the future, perhaps considered a precognition. "Precognition refers to perception that involves the acquisition of future information that cannot be deduced from presently available and normally acquired sense-based information." (Wikipedia)
So I would say that Déjà vu, seen already, would be a feeling. More scientifically, it is when your long term memory and your brains perception of the present moment overlap, malfunction. This is where we play the guessing game following where ideas and facts point us to try to make a conclusion. But let me first make a rabbit trail:
The human race is a three dimensional race, we exist within time, where as a four dimensional race would exist outside of time (that is if we all still agree that time is the fourth dimension). Because our minds think of time as a progression that is in motion and cannot be altered, we will always see time as just that. We will always see time as the past having happened, the present happening, and the future going to happen. And, of course, that is how it has, does, and will happen - as we perceive it. But we are also trapped in existing only in the present, where as a four dimensional being would exist in the present, past and future presumably unchanged.
I am sure that my description of the dimensions in which we exist in is not entirely adequate for the argument that I intend to make, but if I do eventually elaborate my argument and research the topic further, I will also elaborate and research the dimension of time further.
So, if déjà vu is combining our minds perception of the past and the present, if they are overlapping or malfunctioning, perhaps we are launched for that small amount of time into being four dimensional creatures. Perhaps because of our perception of the present and the past being altered, our minds will activate a new part of the brain, a part unused, that allows us to glimpse into the future.
You may think that if this were possible then by now we would all know all about the future and past. But the fact remains that we are three dimensional creatures, that our minds function naturally in three dimensions. So in this time of our brains malfunctioning, I propose that our minds are ultimately looking at the present, and because we are living outside of time for the moment, our mind does not see this as a "new" occurrence. If we exist outside of time, then nothing is actually new; nothing actually happens that we don't already know about.
So perhaps I am correct so far, perhaps déjà vu feels so strange because we are actually being propelled into the fourth dimension. What then is happening when someone can predict the next occurrence to happen while in this moment of déjà vu? I propose this to be an insight to the future. We are launched into the fourth dimension, we are launched outside of time, there is no past or present, there simply is existence. When we are launched into this, we have the ability to look at the past or present or future as we so please, but we are three dimensional creatures so we do not actually direct our attention to anything but the present. We are so accustomed to looking at the present that we do not look towards the past or future, but when we are in the fourth dimension perhaps we occur a peripheral vision of time.
When you are staring intently at one thing, you cannot help but observe what is in your peripherals. When your mind, when existing outside of time, is looking at the present, perhaps our "peripheral vision of time" sees the slight events of the future.
So you are shot into a moment of your brain malfunctioning, so the current moment feels like it has happened before because it simply has happened, or is happened. A moment, observed from the exterior perspective of time, simply happens. It never has happened or is happening or will happen, but rather it simply happens or exists. So it would make sense that this moment happening would not appear to be new, because it isn't happening now, but rather it happens, that moment exists. And when you are shot into this strange phenomenon, you see - though limitedly because your mind naturally stares at the moment perceived to be the present - all the future moments that exist and all the past moments that exist. You see the cup falling, then when you are pulled back to the three dimensional world, the cup falls. You see the moment existing from four dimensions, and see it happen from three dimensions.
I apologize for the awful job that this post does in explaining what my thoughts are, but this was written in 30 minutes when it ought to take me 20 more pages and 2 more years to write. But this is the generic idea that we perceive as déjà vu.
