How logically rigorous is the claim that neurochemical changes in the brain 'cause' mood or emotional disorders? Does a running nose cause a cold? In any case, before prescribing powerful chemicals to emotionally distressed patients shouldn't doctors use some sort of machine to test the chemical levels of their brains?

You're right: we shouldn't throw the word "causes" around too casually. Let's fix on depression as our example, and let's keep in mind that simply being sad isn't the same as being clinically depressed. On the one hand, neurochemicals probably aren't just symptoms of depression; they probably have something to do with causing the symptoms -- the listlessness or anxiety, or excessive rumination or protacted feelings of sadness. Perhaps it would be more accurate to say that clinical depression is , at bottom, a malfunction in the neurochemical system, though this may be too reductionistic, and it also may turn out not to get the biology right. But perhaps what you're pointing to is that it still makes sense to ask what causes this malfunction in the first place. That's obviously a very good question. My impression is that sometimes life circumstances can trigger depression, but sometimes there's no clear external cause. The right answer here is likely to be very complicated. At the moment, far as I...

I want to compare the human mind to a computer program, for the sake of this question. In a computer program, if a circumstance occurs that the machine can not process due to a fault in the code, or a lack of processing power, or any number of reasons, the program will error out. It can have many symptoms: frozen program interface, the dreaded blue screen of death, or a simple restart. But either way the program ceases to function. (Of course their are nifty programmers out their that protect against simple errors by allowing a tolerated amount of them go unnoticed if they don't impede the overall abilities of the program.) What I want to know is how or mind deals with these errors. What stops us from running infinite loops that stalls out our minds and rends us slobbering piles of useless flesh. When we are confronted with something that our brain can not understand or grasp or comprehend, how do we cope? Or is there a limit to where we cease to function?

An intriguing puzzle. The first point is that insofar as it's a question about how our minds actually work, it's an empirical matter, and the answer depends on the facts. But there's a design-level issue here (which I'm hoping my better-informed colleagues might chime in on.) Suppose we have a complicated program that's broken up into sub-programs, or modules. And suppose that there is one module whose job it is to monitor what's going on in various other modules and stop them if they appear to be running amok. Perhaps, for example, this monitor module will kill a process if it has cycled through a million iterations without halting. You no doubt get the idea (and may well have thought of it yourself.) If a system is modular enough, and if it has enough safeguards, redundancies, monitoring modules and so on built in, then the chance that it will just go nuts might be small. And so if the mind is essentially a computer, it may be that millions of years of evolution have built it in this sort of...

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