Following on from my last posting "Are we alone in the Universe?" (please read that firstly) - let us now examine the hypothesis that intelligent life from other parts of the Universe have in the past or in the present been showing up on our doorstep on Earth. It is one of the two simplest explanations for the Fermi Paradox - and from logic very often the simplest explanations are the correct ones (refer to Occam's Razor)! Note: the other simple explanation of course would be that there is no intelligent life out there capable of contacting us.
So let's deal with the hypothesis that there is extra-terrestrial intelligent life which is already here. How come we don't know that they are here or have been here? Why would they not try to communicate with us? There seems to be only two possible simple general answers to the above:
A. The intelligent life does not want us to know they are here.
B. The intelligent life is in contact with us but we do not properly realize it.
The proposition in A seems a little weak. Why would the life form be here and not want to communicate with us? Are they just studying us, or afraid of our aggression? It just doesn't seem to add up for an advanced life form to behave this way. It is not likely to be the way we ourselves would behave if we encountered an intelligent race. Historically we would be more likely to give them a lot of trouble in fact!
Let us look at B. If aliens are in contact with us already the first thing to note is that they do not appear to be trying or succeeding in harming us. This would seem compatible with a very advanced intelligent life form. But why do we not realize that super-advanced creatures are in contact with us? This is a very difficult question. We need to perhaps examine evidence of unexplained phenomena on Earth related loosely to other extra-terrestrial life forms.
The obvious place to start is in the whole UFO phenomena. A huge proportion of sightings and encounters seem to be complete rubbish. If there are physical spacecraft and beings which in the present or in the past have visited the Earth then we have never been able to scientifically prove their existence. Also, if they are in such physical form - then why not just come clean and communicate with us properly. Nevertheless, it does remain possible that some kind of relatively advanced alien creatures have made some limited attempts to physically study or communicate with us. It just seems that their efforts have at the very least been unconvincing.
The next thing to examine is what we might refer to as the whole spiritual world. There is huge anecdotal evidence from us humans of all types of spiritual phenomena - from experiences of what we call God to simpler paranormal events. Is it possible that with very advanced knowledge of the nature of matter and energy that we could in the future transcend our existence into some other format? We are discovering more and more about subatomic particles and the fabric of matter and energy and perhaps we will discover other startling things which we can control in the future. Is it possible that we can become immortal in the future by becoming what we might loosely today call pure spirits? Maybe it's already happening without us properly understanding it.
The other thing to keep an open mind on is that spiritual existence may not have a strong relationship with physical space and time as we see it. So in other words these aliens may not relate directly in their advanced state to any physical part of the Universe. They may never even have existed as physical bodies as we are or they may have learned how to transcend and then have no meaning in terms of physical location.
The Universe is physically so vast that it would seem to take a massive and fundamental breakthrough in the nature of a being's existence in order to communicate throughout the Universe. The physical Universe is effectively impossible to explore on any sensible scale by planet-based physical creatures that depend on resources of the planet to stay alive.
From the above brief thought process it could be speculated that alien intelligence is more likely to be communicating with our minds or souls/spirits than actually physically appearing in front of us. We can live with the idea of "mind" perhaps but the concept of a soul or spirit in a proper scientific sense is still very advanced for us to work with. However in my opinion we need to start thinking of advanced alien civilizations communicating with us in ways related to this. In a massive physical Universe it is the only way I can see that can make sense of a positive answer to the Fermi Paradox.
To take my "They're here!" hypothesis much further is tempting but of course extremely speculative. One could start to argue that what we would call God is actually a very advanced spiritual life form that is trying to communicate and help us. I want to resist going much further with this as we are now really moving the wagon wheels deep into the Injun territory of non sequitur!
It is difficult to analyze this subject objectively in a detailed way, we don't seem to have the tools and indeed it's not even a faculty of regular science. However, it is time that we started to merge humanity's diverse and large pools of knowledge in physical sciences, philosophy, logic, religion and even the paranormal into a new form of super-science. This super-science may be fundamental to our understanding of ourselves and the nature of life everywhere in the Universe. Without doubt it could be the most important subject we ever study.