As always (or, at least, as for some time now) I read Dr C's information Some Thoughts on Information - IV with great interest but without the competence to provide much in the way of relevant comment or reply. So, as usual, after enjoying both the content and the references (those animations, for example), I went off at tangents.
For instance, I mused over a couple of things in the "review of the story so far". I would have been tempted to say that the brain is completely dependent, rather than "strongly dependent", on sensory information received. Even when surviving sensory deprivation, it falls back on recycling of external information previously received.
And I was amused by his use of the word "purpose" ("In spite of being in thrall to the imagination, I am sure you will agree that abstract creativity is not the primary purpose of the brain" - para 3, my emphasis). It is, of course, a figure of speech: I use it myself. My amusement derives from knowing that Dr C is usually more strict than I about not using language which imputes purpose to the products of blind evolutionary chance. Amusement aside, this says more about language, and thinking, and the symbolic bases of both, than about Dr C or myself.
Unashamedly picking up and using that word, purpose, in the same sense and spirit as Dr C, I do wonder whether I can really agree that abstract creativity is not the primary purpose of the brain. I emphasise, before continuing, that I am not a medical, neurochemical, or any other flavour of life scientist: I view this from a systems point of view, making a lay person's use (or possibly unintentional abuse) of information gleaned from others. Given that caveat, it seems to me that the brain is not a single entity which can be said to have a single primary purpose.
If there is such a thing as the unitary primary purpose of the brain, however, then I imagine that it would be something along the lines of "maximising probability of survival, wellbeing and procreation for the organism of which it is part". Exactly how that probability is maximised is, however, a complex question. The oldest parts of the brain, the first to evolve, doubtless interpret this as maintaining internal biological functions and capability for fight or flight. Newer areas, though, have evolved to meet more sophisticated needs.
Abstract creativity is the faculty which makes possible concrete problem solving in unexpected and unpredictable (even, on occasion, unimaginable) sets of new conditions or circumstances. It is at least arguable as a hypothesis that capacity for abstract creativity is the main factor in maximising the probability of survival, wellbeing and procreation for Homo sapiens. And if that hypothesis is accepted, then can it not be said that abstract creativity is the primary purpose (or at least a primary purpose) of the newest, most recently evolved regions of the brain?
I suspect that by asking that question I expose myself to an answer which shows my reasoning to be wanting...