I was interpreting the "or purpose" in this case as a basic synonym for meaning, but I can see that that may not have been intended. I think I was driven by the statement that:
"Through evolutionary conditioning, you are blind to the lack of point of living."
I took this as an indication that gurgeh was talking about subjective meaning, but that assumes that's where most people find their "point of living", or even where they can perceive a point in living once their belief in objective meaning is no longer. If you only found your point in living in inherent meaning, or didn't like the idea of just choosing or falling into having a meaning, then I could see gurgeh's statement being more disturbing.
In relation to your last comment, I'm interested in that occasionally mentioned apparent opposition between "cold hard science" and "the wonder and beauty of life" and all that. I'm not assuming you feel this way, but many find the idea that all meaning in our lives is the result of ion channels and patterns of activation to be disheartening and at odds with things like beautiful literature, meditation, or love. Personally I don't perceive any opposition and this doesn't bother me in the slightest, if anything it just increases my fascination with the human brain. If it's that perceived dichotomy that is the primary reason for saying that long or clear contemplation brings depression, I say: A rose by any other name...
I am not disheartened by the physics and biology of mind, nor do I see any particular conflict between science and beauty (but I typically find more beauty in manmade machinery than forests).
I was being somewhat facetious about "become clinically depressed". Ultimately, I, like everyone else, do what I want to do because I want to do that. However, I have a longing for something more meaningful than that, for something that is bigger than myself, for something I can live for that means something even if I die. I can feel the pull of service ...
Human beings are all crazy. And if you tap on our brains just a little, we get so crazy that even other humans notice. Anosognosics are one of my favorite examples of this; people with right-hemisphere damage whose left arms become paralyzed, and who deny that their left arms are paralyzed, coming up with excuses whenever they're asked why they can't move their arms.
A truly wonderful form of brain damage - it disables your ability to notice or accept the brain damage. If you're told outright that your arm is paralyzed, you'll deny it. All the marvelous excuse-generating rationalization faculties of the brain will be mobilized to mask the damage from your own sight. As Yvain summarized:
I find it disturbing that the brain has such a simple macro for absolute denial that it can be invoked as a side effect of paralysis. That a single whack on the brain can both disable a left-side motor function, and disable our ability to recognize or accept the disability. Other forms of brain damage also seem to both cause insanity and disallow recognition of that insanity - for example, when people insist that their friends have been replaced by exact duplicates after damage to face-recognizing areas.
And it really makes you wonder...
...what if we all have some form of brain damage in common, so that none of us notice some simple and obvious fact? As blatant, perhaps, as our left arms being paralyzed? Every time this fact intrudes into our universe, we come up with some ridiculous excuse to dismiss it - as ridiculous as "It's my daughter's arm" - only there's no sane doctor watching to pursue the argument any further. (Would we all come up with the same excuse?)
If the "absolute denial macro" is that simple, and invoked that easily...
Now, suppose you built an AI. You wrote the source code yourself, and so far as you can tell by inspecting the AI's thought processes, it has no equivalent of the "absolute denial macro" - there's no point damage that could inflict on it the equivalent of anosognosia. It has redundant differently-architected systems, defending in depth against cognitive errors. If one system makes a mistake, two others will catch it. The AI has no functionality at all for deliberate rationalization, let alone the doublethink and denial-of-denial that characterizes anosognosics or humans thinking about politics. Inspecting the AI's thought processes seems to show that, in accordance with your design, the AI has no intention to deceive you, and an explicit goal of telling you the truth. And in your experience so far, the AI has been, inhumanly, well-calibrated; the AI has assigned 99% certainty on a couple of hundred occasions, and been wrong exactly twice that you know of.
Arguably, you now have far better reason to trust what the AI says to you, than to trust your own thoughts.
And now the AI tells you that it's 99.9% sure - having seen it with its own cameras, and confirmed from a hundred other sources - even though (it thinks) the human brain is built to invoke the absolute denial macro on it - that...
...what?
What's the craziest thing the AI could tell you, such that you would be willing to believe that the AI was the sane one?
(Some of my own answers appear in the comments.)