Consciousness depends, it turns out, on how different parts of the brain speak to one another.
Marcello Massimini at the University of Milan has done some important studies, stimulating the brain with brief pulses of energy for the purpose of studying its response in different conditions. This is known as transcranial magnetic stimulation.
The TMS work indicates that in dreamless sleep and under general anaesthesia, the brain "echoes" the magnetic pulse in a simple way.
But ... apply the pulse to the brain of someone fully conscious, and the echoes are much more complicated, disappearing from one part of the organ and re-appearing in a complex way that seems to suggest the parts are communicating with one another about this new thing.
How can one measure the "complexity" of an echo? I don't know, because I'm not an IT guy. But I gather the means of measurement involves compressibility, something like the way digital photos are compressed into JPEG files. So perhaps we are more or less conscious throughout our waking day, or during a dream, in a way correlated with this complexity, and Massimini has invented a consciousness meter.
One of the points that Lovejoy makes in the book of that title I mentioned last week is the importance, in the Neo-Platonist conceptions and in the later development of the "chain of being" metaphor, of what he calls the principle of plenitude. This is the underlying notion that everything that can exist must exist, that creation would not be possible at all were it to leave gaps.
The value of this idea for a certain type of theodicy is clear enough.
This caused theological difficulties when these ideas were absorbed into Christianity. I'll quote a bit of what Lovejoy has to say about those difficulties:
"For that conception, when taken over into Christianity, had to be accommodated to very different principles, drawn from other sources, which forbade its literal interpretation; to carry it through to what seemed to be its necessary implications was to be sure of falling into one theological pitfall or another."
This is a quote from a memoir by Dorothy Wordsworth, reflecting on a trip she took with two famous poets, her brother, William Wordsworth, and their similarly gifted companion, Samuel Taylor Coleridge.
We sat upon a bench, placed for the sake of one of these views, whence we looked down upon the waterfall, and over the open country ... A lady and gentleman, more expeditious tourists than ourselves, came to the spot; they left us at the seat, and we found them again at another station above the Falls. Coleridge, who is always good-natured enough to enter into conversation with anybody whom he meets in his way, began to talk with the gentleman, who observed that it was a majestic waterfall. Coleridge was delighted with the accuracy of the epithet, particularly as he had been settling in his own mind the precise meaning of the words grand, majestic, sublime, etc., and had discussed the subject with William at some length the day before. “Yes, sir,” says Coleridge, “it is a majestic wate…