Reason must be rationally inferred or it is no longer valid.
That seems somewhat tautological - reasoning is how rational arguments are made.
A system of information processing can be based on irrational statements, such as a madman interpreting a streetlamp as an alien spaceship or a computer programme interpreting on or off circuits. These do not necessarily infer consequent propositions, although the latter can certainly be used in a representational method to facilitate reasoning, the information processing is not Reason per se.
It seems to me that reasoning is effectively making conclusions from a valid argument; regardless of the truth of the premises, if the conclusion is reached through valid argument, it has been reasoned. If the premises are true, the argument will be sound and the reasoned conclusion will be true. If one or more premises are false, the argument will not be sound and the reasoned conclusion will be false although correctly reasoned. In other words, in both cases, reason is used to argue correctly given the premises, but the conclusion will only certainly be true if the premises are true.
I tried to explain it earlier with formal propositions to you, if you wouldn't mind taking a gander at that post again?
Yes, I don't agree with your first (compound) premise. I agree that reasoning requires insight or understanding of the logical relations between the premises - that's how a valid argument is constructed; but I don't agree that neurons firing in the head cannot be the underlying cause of insight or understanding. It may turn on how one defines insight or understanding, and/or what kind of information processor can achieve them. But I also think there's an implicit appeal to incredulity in phrases like, "neurons firing in the head". But then, who would believe transistors switching in microchips could beat the world's best human competitors at the verbal quiz game 'Jeopardy'? Who would imagine that a simple static grid of cells that can be black or white ('on' or 'off') depending on the on/off states of neighboring cells (i.e.
Conway's Game of Life cellular automaton) could
emulate a computer (universal Turing machine), or make a
self-replicating structure, or
emulate itself? The interactions of simple parts can give rise to exceedingly complex behaviours.
'Neurons firing in the head' produce a range of informational structures, from content-addressable storage (memory) and associative mapping of that storage, to inductive and deductive logic processing, that can be used to facilitate understanding and insight. High-level systems such as those involving the self and language understanding, are composed of subsystems, and those of smaller subsystems, and so-on to the neuronal level. In the brain the hierarchy is not rigid - subsystems are shared and cross-connected, and there are competing 'opponent' systems down to the individual neurons.
...someone being scared of a tiger is logical. But if he is scared of a tiger ultimately because he believes alien souls inhabit it, then it is not logical..
No, it's quite logical to be scared of a tiger if you think it's inhabited by alien souls and you're afraid of alien souls; it's the premises that are false. It's also quite rational to scared, given that premise (i.e. that belief). It's the belief that's irrational, not the reasoning based on it.
... but taken to be logical if his full reasoning, the full panoply of propositions, was not investigated.
It's not the truth or falsity of the premises that make an argument logical (valid). When true, they make a valid argument sound.
We cannot even show how neuronal activity in Wernicke's area can make us understand the written word. We assume it does, but we cannot point to a mechanism whereby neuron depolarisation bequeths us understanding. It is clear that language processing lies here, for it disappears if damaged, but we cannot say it is due to neural networks depolarising in a certain way or not.
Last I heard, Wernicke's area is mainly involved in the phonetic and syntactic aspects of language, recognition and parsing; the full understanding of meaning is distributed across the cortex, as one might expect.
The brain requires quite a lot of comprehensive explanation.
A lot of work has already been done - parts of some systems have been comprehensively explained (e.g. parts of the visual system), and others functionally mapped in considerable detail. Sure, there's a lot more to do than has yet been done, but with in excess of 80 billion components, it's a complex system.
The cases are not as clear cut as you present in anyway. Maybe one or two case studies exist, but you will see these have not been repeatable in most cases. If I am wrong and you have access to such studies, please supply them, as I would be very interested.
I don't have links for them, although they're probably online - I learned of them from books (e.g. by V.S. Ramachandran) and conferences. One example of a very specific deficit was a man who had a stroke and ceased to be able to recognise items. He couldn't recognise himself or anyone he knew, and he couldn't recognise objects, although he knew what type of objects they were and could describe them in detail. For example, when shown a carrot, he knew it was a vegetable, and described it accurately, but he didn't know what vegetable it was; on the other hand he could also tell you all about carrots, their appearance, growth, use, etc. When asked to draw a selection of flowers, he made drawings labelled 'rose', 'tulip', 'daffodil', etc, but he drew imaginary flower shapes, nothing like the real thing, and yet he could accurately describe the features of the real flowers. Then there's Capgras' syndrome, where someone thinks their partner has been replaced by an identical imposter; believed to be due to damage to communication between the recognition & discrimination centre in the fusiform gyrus and the emotional limbic system (the amygdala). Another oddly specific one is 'Telephone syndrome', where individuals are in an apparently minimally conscious state, showing sleep/wake cycles and eye tracking, but unresponsive and uncommunicative - until they're given a phone call, when they suddenly become fully conscious, alert, and normally communicative, only to subside back to unresponsiveness afterwards, even to the same person that called them. Another is paralysis denial, where the individual is paralysed in some way, but denies it and attempts tasks requiring the paralysed limb, claiming success, or making unrelated excuses, when they fail dismally; there's a disconnect between their physical state and their brain's body map, making them unaware of the paralysis and unable to learn of it. Similarly, there's hemispherical neglect, where the left or right half of the person's perceptual experience is absent (i.e. half their perceptual world), although all the perceptual pathways are intact.
