And I wouldn't call it preposterous.
Aside from his entire paper... I'd like to focus on just the main aspect.
Dick asserts that what we claim to be "knowledge" is actually a mental picture of reality that was brought about by our sensory perception. However, without fully understanding the processes at work in our sensory network, we can never know what is ACTUALLY going on. We study the laws of physics, but we use our senses to observe and experiment. Well how can we rely so faithfully on our "sensory perception" to reveal the secrets of the universe, when we don't even know how sensory perception operates? Sure one could say that our senses are a byproduct of physical processes fully explained by the laws of physics. This gets us right back to square one! Can we trust our senses to reveal the truth about nature? Well only if we can trust the "method" by which they work. The rules would be governed by the laws of physics, and yet we can't know what the laws are, without first observing nature at work (via senses). It's a logic trap...
How do we know what the laws of physics are...?
"Well we just have to trust our senses when it comes to extracting information via experimentation."
How do we know we can trust our senses...?
"Because those are the ONLY means by which one can observe the universe. Therefore, either we trust our senses and move on, or we don't and we are forever questioning knowledge of reality."
How do we separate "truth" from "illusion"?
"It takes many intuitive 'leaps of assumption' and minds capable of looking at life from a different perspective. These leaps are consequently subjected to rigorous testing and verification beyond all doubt. Those are the people we turn to for answers; the people that think "outside of the box". These are known as the worlds genius scientists, mathematicians, philosophers, etc."
We trust our senses to observe nature, but without knowing how our senses actually turn observation into a useful mental picture. Afterall, it is this final interpretive process that ultimately is deemed "knowledge", and yet, we don't even know how this mental/sensory communication network operates. We must "watch" nature... mentally interpret our observations... and finally separate "truth" from "misconception" and misleading implied-assumption.
How do we know actual "truth" ever even materializes? For that we must trust our brain, and yet our brain has been known to play tricks on us (go to your local bookstore and check it out; there are plenty of pictures that play tricks on your mind due to illusion).
Often times the laws of physics turn out to be counterintuitive; meaning we can't even trust our mental picture to be accurate (for example particle-wave duality and quantum "madness") We learn that the macroscopic life we grow up in and become so accustomed to living, just isn't real. Everyday life is just an illusion accredited to the spectral EXTREMITIES of Planck's constant h (far left end of the spectrum) and Einstein's constant c (far right end of the spectrum). Let's face it... because of the extreme largeness of c and extreme minuteness of h, our senses are simply not calibrated sensitive enough to notice "reality" happening right under our noses. Relativity is only noticeable with ridiculously high velocities, and h is only noticeable with ridiculously small dimension scales. This goes to show that there may be a multitude of misconceptions that we humans have been unable to as-of-yet produce the proper genius(es), to look at from a skewed perspective and uncover.
Science never fails to show us that we are living an illusion. We can't always trust our senses... so we are in need of a "theory of sensory perception". However such a theory would require that we use our current method of scientific investigation of nature (which ironically we must use the very senses that we are questioning!). Our current method seems to be the only way... so there is no way around this blockade! Afterall, how do you collect and interpret information without using one or more of your five senses? How do we really know that we know anything? What is knowledge? That which we think we know, or is there an actual platonic truth that we slowly uncover piece by piece?
Mathematics would appear to be "knowledge" in its purest most powerful form... Pure logic is seemingly unadulterated by pesky illusions. The question is... how do we incorporate a fully mathematical view of the world, unadulterated by misleading assumptions and everyday life intuition? I believe Dick goes on to cover all of this in his writings, but I have a different approach.
My approach would go along the lines that perhaps it is IMPOSSIBLE to have a complete theory of nature and hence unquestionable truth. Of course this is nothing new, but perhaps the way I arrived at it is original. If I remember correctly, Dick may have alluded to this notion indirectly or somewhat, but I intend to attack the problem at slightly different angle!
I didn't read his whole paper, so forgive me if I unduly take credit for what I thought was an original idea. When I have the time, I'll read his paper more thoroughly. Also... I'll post my own idea at a later time if you'd like to see it.
Thanx for your time,