IllegalArgument said:
I hate to ask but what do you mean by "mind" then if not the brain?
How about optical illusions? Do they show that the brain has limitations?
What do I mean by mind... hm. That's one of the tougher questions around here. I'll try to answer it as briefly as reasonable.
I equate "mind" to self-consciousness, self-awareness, reason, mental imagery, and emotion. All of these processes (and probably more that I haven't thought of) combined make up the human "mind". Are these processes purely physical? That, I think, is part of the debate.
It's possible to have a apparently physically intact brain without having a mind. Granted, the brain doesn't reflect "normal" electrical activity - but that's not the same thing as having a physically damaged or inoperable brain. However, it's impossible to have a mind without a brain... so it would seem clear that there's a kind of one-way dependency between the two. (Stating the obvious, I know.)
But - if one can have an intact brain without having a mind... that would seem to open the door to the converse thought that the mind - while dependent on the physical brain -
may exist in a way other than purely physical. Else why would an otherwise perfectly useable brain fail to have a mind active in it? I believe we are forced to assume that there's something else going on that we don't fully understand... which is why research on the human brain and mind is ongoing.
Effectively all I'm really saying is that there's enough unanswered questions for me to be uncertain about this. Thus I differentiate between the brain and the mind. (At this time.

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Regarding your second question - you can either view optical illusions as a limitation or a demonstration of a lack of limits. If the illusion is perfect, then there is no demonstration of limitations, because a perfect optical illusion is indistiguishable from reality.
If the illusion is NOT perfect (and very few are!), then one can say that the mind failed to interpret the data from the senses properly, which would indeed demonstrate a limitation - but is it one of the mind, or of the senses? Hard to say.
Alternatively, one can say that the mind filled in the gaps where the illusion failed to be perfect. In this case, that's quite the reverse of a constraint - it shows a great deal of ability instead.
Just my take on it, of course, and I'm tired, and going to bed... so I hope what I wrote makes some kind of sense. I'm too tired to tell.
