It seems your question was not really answered. You seem to be asking, if we have an immaterial mind then why do we need a brain at all? The answer is that the immaterial mind/soul is inhabiting a body/brain, and so long as it does so, it requires an appropriate apparatus through which to operate.

We are not disembodied, we are embodied.

As to those folks with half a brain and normal function – well it’s a strange world, isn’t it?

A new article appeared only one hour ago on SciAM about neglected human Glial cells that comprise 90% of human brain.

http://www.scientificamerican......ought-what

It is curious that those who think the difference between humans and other species is immaterial should be so concerned to find material differences to justify the difference.

In an earlier post, Barb mentioned Broca’s area as a region of the brain that differentiates us from other animals. I thought I’d do a little digging and delving, and here’s what I’ve come up with.

Attention Denyse:
While doing this research, I came across a very interesting blog called Not a Chimp by former BBC science producer Jeremy Taylor, who has made numerous television programmes informed by evolutionary theory, including two with Richard Dawkins. Taylor argues in his blog that argues that the similarities between humans and chimps “have been grossly over-exaggerated” and suggest that maybe “humans [are] cognitively unique after all.” Taylor’s preface makes for fascinating reading.

Getting back to Broca’s area. Readers might like to check out this blog by Taylor on Broca’s area, which, although it occurs in other primates, is strikingly different in human beings:

Why Humans Talk And Chimps Don’t

It’s a fertile time, at the moment, for interesting comparative functional neuroscience! Here an article reports on recent work on Broca’s Area, by Chet Sherwood and team. They sectioned and examined Broca’s Area from a dozen chimps and discovered that there is no left-right asymmetry in terms of number of neurons and that there were a lot of individual differences in the size, location and symmetry of Broca’s Area, rather than a pan-species norm – as exists in humans. Neither was the handedness of the chimps in any way related to symmetry of Broca’s (Broca’s Area in chimps has been related to the use of hand gestures and tool use). Furthermore, they notice that, while the human brain in total is some 3.6 times larger than the chimp brain, Broca’s Area in the human is 6 times larger than in the chimp. It has ballooned in the human lineage. . (Emphases mine – VJT.)

Readers who want to access the original article might like to have a look at this abstract from Cerebral Cortex Advance Access, published online on July 20, 2009. Cerebral Cortex, doi:10.1093/cercor/bhp138. Web address:
http://cercor.oxfordjournals.o.....t/bhp138v1

Broca’s Area Homologue in Chimpanzees (Pan troglodytes): Probabilistic Mapping, Asymmetry, and Comparison to Humans
by Natalie M. Schenker William D. Hopkins, Muhammad A. Spocter, Amy R. Garrison, Cheryl D. Stimpson, Joseph M. Erwin, Patrick R. Hof and Chet C. Sherwood

Abstract:

Neural changes that occurred during human evolution to support language are poorly understood. As a basis of comparison to humans, we used design-based stereological methods to estimate volumes, total neuron numbers, and neuron densities in Brodmann’s areas 44 and 45 in both cerebral hemispheres of 12 chimpanzees (Pan troglodytes), one of our species’ closest living relatives. We found that the degree of interindividual variation in the topographic location and quantitative cytoarchitecture of areas 44 and 45 in chimpanzees was comparable to that seen in humans from previous studies. However, in contrast to the documented asymmetries in humans, we did not find significant population-level hemispheric asymmetry for any measures of areas 44 and 45 in chimpanzees. Furthermore, there was no relationship between asymmetries of stereological data and magnetic resonance imaging–based measures of inferior frontal gyrus morphology or hand preference on 2 different behavioral tasks. These findings suggest that Broca’s area in the left hemisphere expanded in relative size during human evolution, possibly as an adaptation for our species’ language abilities. (Emphases mine – VJT.)

……………………………

Here’s another paper on the analogue of Broca’s area in macaque monkeys. The authors mention in passing that asymmetry in Broca’s cap has been found in endocasts of Homo erectus skulls, suggesting that various parts of the brain were falling into place before manifesting themselves, much more recently, in a language faculty.

Petrides M, Pandya DN, 2009. Distinct Parietal and Temporal Pathways to the Homologues of Broca’s Area in the Monkey. In PLoS Biology 7(8): e1000170. doi:10.1371/journal.pbio.1000170
at http://www.plosbiology.org/art.....io.1000170

The homologues of the two distinct architectonic areas 44 and 45 that constitute the anterior language zone (Broca’s region) in the human ventrolateral frontal lobe were recently established in the macaque monkey….

Two distinct cortical areas in the frontal lobe of the human brain, known as Broca’s region, are involved with language production. This region has also been shown to exist in nonhuman primates. In this study, we explored the precise neural connectivity of Broca’s region in macaque monkeys using the autoradiographic method to achieve a level of detail impossible in the human brain… We suggest that a fundamental function of Broca’s region is to retrieve information in a controlled strategic way from posterior cortical regions and to translate this information into action. This fundamental function was adapted during evolution of the left hemisphere of the human brain to serve language…

Our suggestion here is simply that an area that served higher control of action in the macaque monkey may have been adapted for the control of complex hierarchical sequences of gestural and vocal action with the evolution of communication leading to human speech.

When might this adaptation have begun? There is paleoneurological evidence from fossil endocasts that the asymmetry in Broca’s region observed in the modern human brain can be observed in brain endocasts of specimens assigned to Homo erectus/habilis, based on the petalia impressions [65] and the study of the endocast of the Sambungmacan 3 (Sm3) fossil, a Homo erectus calvaria from Indonesia [66]. For instance, Sm3 exhibits left-right cerebral volume asymmetry and marked asymmetry in Broca’s cap, i.e., modern human characteristics. Thus, the fossil evidence suggests that this asymmetry is a relatively recent event in the evolution of the human brain. (Emphases mine – VJT.)

Think science has it all sewn up, now? Think again. Here’s an extract from the Wikipedia article on Broca’s area:

Speaking without Broca’s area

The essential role of the Broca’s area in speech production has been questioned since it can be destroyed while leaving language nearly intact. In one case of a computer engineer a slow growing glioma was removed. The tumor and the surgery destroyed the left inferior and middle frontal gyrus, the head of the caudate nucleus, the anterior limb of the internal capsule and the anterior insula. However there were minimal language problems three months after removal and the individual returned to his professional work. These minor problems include the inability to create syntactically complex sentences … including more than two subjects, multiple causal conjunctions or reported speech. These were explained by researchers as due to working memory problems. They also attributed his lack of problems to extensive compensatory mechanisms enabled by neural plasticity in nearby cerebral cortex and a shift of some functions to the homologous area in the right hemisphere. (Emphases mine – VJT.)

Here’s the reference:
Plaza M, Gatignol P, Leroy M, Duffau H. (2009). Speaking without Broca’s area after tumor resection. In Neurocase 9:1-17. PMID 19274574.
http://www.ncbi.nlm.nih.gov/pubmed/19274574

And on a lighter note, from MSNBC:

Dogs (not chimps) most like humans: Man’s best friend serves as model for understanding human social behavior by Jennifer Viegas (March 26, 2009) at
http://www.msnbc.msn.com/id/29895614/

Just a couple of quick comments. You wrote:

To regard a purely material entity as choosing would require a different brand of materialism than any I know. Scientifically, it seems that willful action in a material system would violate conservation of mass and energy.

I suppose that if you wanted to be a “free-will” materialist in the libertarian sense, you would have to reject not only determinism but also reductionism. You would have to say that matter, suitably configured, has some top-down properties which are not reducible to or predictable from its constituents – and that free will is one of these strange properties.

I suppose that’s a logically tenable option, although as J. P. Moreland observed when Lee Strobel asked him a similar question in chapter 10 of his book The Case for a Creator, it is a rather strange view, as it would involve imputing psychic properties to matter.

Regarding the law of conservation of mass-energy: that is the least of dualism’s worries. One need not imagine that an immaterial mind suddenly reaches into the material realm out of the blue and pushes neurons around; all that need take place is that energy is either redistributed from one place to another, or alternatively converted from one form (e.g. chemical potential energy) to another kinetic energy).

I don’t know much about the conservation of information, but I believe that Professor Behe has suggested that the information needed to create life could have been programmed into the universe from the very beginning.

Very interesting, indeed:

In answer to your question, it may interest you to know that there are Christians [Christadelphians and Jehovah's Witnesses] who believe life on Earth had a Designer, and who believe that human beings were created in God’s image with mental capacities that are unique and utterly distinct from those of animals, but who also believe that human beings are purely material entities who do not possess an immaterial soul and therefore do not survive bodily death, but who will nevertheless be resurrected on Judgement Day, with an immortal body, provided that they acknowledge, honor and serve their Creator.

I’m unfamiliar with the Christadelphians, so I’ll stick with Jehovah’s Witnesses, who do not believe that God has preordained who will live in the earthly paradise. It follows that people purposefully create their own behaviors by acts of will. To regard a purely material entity as choosing would require a different brand of materialism than any I know. Scientifically, it seems that willful action in a material system would violate conservation of mass and energy.

Of course, some leading proponents of ID say that not only mass and energy, but also physical information, is conserved in the action of strictly material systems, and that design information is purposefully created by immaterial intelligence. A weakness here is that there is no answer to the question of how the design created by an immaterial intelligence results in configuration of matter. The design must somehow jump the gap between the immaterial and the material. Work must occur to configure matter according to the design.

What I see in your comment is that someone with unpopular religious beliefs might devise a theory of ID that is more parsimonious than those we commonly see. Rather than dubiously reify information and make the complex claim that a) something unobservable and immaterial creates physical information, and b) information manifests in configurations of matter by unknown means, why not challenge the notion that the laws of conservation of mass and energy are inviolate? The hypothesis that so-called physical law does not apply to certain organizations of matter, including the human brain, actually is considerably less elaborate than prevailing ID theory.

Not really. The article’s sub-headline reads: “More than half of adults in a survey of 10 countries thought school science lessons should teach evolutionary theories alongside creationism.”

Based on what the article actually says, your comment should actually read: “It seems that a slight majority (53%) of people in the world would like creationism to be taught alongside evolution.”

Only later in the article does it mention “…other possible perspectives (than evolution), such as intelligent design and creationism” – but it does not say if some prefer creationism and some prefer intelligent design, nor does it say what percentage prefer which.

There are, however, weighty philosophical reasons for doubting that any materialist account of the human mind could possibly do justice to the way we think. Arguments against the idea that our thoughts are purely physical processes fall into four general categories:

1. Formal Arguments, which are based on special features of mental operations, which preclude our identifying them with material processes:

universality – the fact that we are able to form concepts (e.g. gold) which hold true at all times and places, whereas material processes are time- and place-specific;

infinite cardinality – the fact that we can form infinitely many concepts, whereas a finite brain could only hold a finite number of concepts;

the intentionality or “aboutness” of our thoughts – whenever we think, we think about something, and there are certain rules we have to follow when we do so – but brain states can’t follow rules, and don’t seem to be “about” anything (except in the survivalist sense of being suitably configured for acquiring something you might want);

the formal specificity of our intellectual operations (how can it be meaningful to say that a brain process of type X corresponds to the mental operation of squaring a number and not doubling it, for instance?);

the specific propositional content of our thoughts (e.g. how can a brain state mean “It will rain tomorrow”?);

the complete lack of isomorphism (one-to-one structural correspondence) between our memories and states of affairs in the world; and

the ability of our thoughts and memories to be triggered by indefinitely many different kinds of events in the world, unlike physical processes, which have a finite number of possible causes.

2. Transcendental Arguments, which are based on the reliability of mental operations: if our mental operations were identical with material processes, then we could no longer be sure that our logical arguments were valid or invalid, based purely upon their formal features. But since formal logic is universally valid, that with which we reason cannot be material.

3. Phenomenological Arguments, which are based on the irreducibly first-person features of subjective consciousness: physical states can be exhaustively described in third-person terminology, but if we try to describe our conscious states (e.g. colors, sounds, tastes, smells and feelings) using third-person terminology, we fail to adequately convey their subjective quality; hence conscious states cannot be identified with physical states.

4. Reductio Ad Absurdum Arguments, which endeavor to show that materialism entails absurd consequences, such as the non-existence of a self, or the absence of freedom.

Readers who would like to peruse some good philosophical articles defending these four kinds of arguments can go here and here.

My two cents’ worth: I think arguments of the first and fourth kind are the strongest, and I find it difficult to see how a purely material entity could be said to possess free will, no matter how intricately designed it is.

In answer to your question, it may interest you to know that there are Christians who believe life on Earth had a Designer, and who believe that human beings were created in God’s image with mental capacities that are unique and utterly distinct from those of animals, but who also believe that human beings are purely material entities who do not possess an immaterial soul and therefore do not survive bodily death, but who will nevertheless be resurrected on Judgement Day, with an immortal body, provided that they acknowledge, honor and serve their Creator.

Jehovah’s Witnesses and Christadelphians are two examples of Christians who share these beliefs.

It separates humans from animals, for one thing.

My personal belief is that the expression of intelligence in humans is evidence of a designer (for me, God).