I find myself becoming more and more convinced that we only think when we are faced with a problem that is capable of resolution, and that when we are not engaged in such a task, we simply stop thinking, or perhaps defer thought until we are once more faced with something useful to do. When we're not busy with an actual task, we tend to occupy ourselves with fancies of various sorts, and suffer as a result--unless we understand and accept that we are doing something different from what we do when we think.
I should note that here I'm using "think" in a sense some might consider narrow. I'm not contending that there is no brain activity involved in anything but problem-solving or decision-making. Obviously, we dream, we imagine, we meditate, we do things which don't require the application of intelligence with some frequency, even most of the time. I mean "think" rationally, judging which means are appropriate to result in certain ends, for example, or seeking explanations for phenomena based on an assessment of circumstances and causes and effects. I mean it, in other words, in the way Dewey did in philosophy, and as I think most people involved in completing tasks in ordinary, day-to-day life mean it.
Two things in particular have made me speculate along these line. One is reading the Memoirs of General U. S. Grant (I use his military title as they are memoirs of his military career). His presidency most of us remember as notable for its corruption and its especially haphazard nature. He himself was considered by many to be sullen, morose and given to drink. His Memoirs, however, are very well written. I'm apparently not the first to be impressed by his clear, simple, intelligent style, or to wonder at it given his reputation. He is precise in his narrative, and has a dry, understated wit. He is straightforward; what he deplores (like the Mexican War) he deplores flatly and without qualification; he addresses what he admires in much the same way. It is an admirable book.
He wrote it while dying of cancer, and deeply in debt. He wrote it in the hope its sale would provide for his family when he was gone. He finished it shortly before he died and it sold well, achieving his purpose.
His actions during the Civil War seem also to have been the result of a focused analysis of how to achieve the defeat of the Confederacy in the shortest possible period of time. He did so through the relentless, savage application of superior resources and by the acceptance of the doctrine of "total war" ably assisted by his friend Sherman, who seems to have been intent on demonstrating the truth of his comment that war is all hell.
Given a task to perform or a problem to solve, Grant seems to have thought quite well.
But a greater motivation to ponder this possibility resulted from watching (portions of) a remarkable series on the History Channel entitled Ancient Aliens. It constitutes basically a review (I won't say study) of various ancient ruins and interviews of several sadly well-known advocates of the view that the Earth was visited long ago by extraterrestrials who if they did not themselves create these wondrous monuments assisted or inspired our dull, ignorant ancestors sufficiently enough to assure their creation. I'm something of an archaeology buff, and am ashamed to report it was through this series that I first became familiar with the site of Pumapunku (or Puma Punku or Puma Punka, it seems) in Bolivia, which those luminaries interviewed contend is incredibly old (15,000 years) and could only have been built through use of machines and only planned by people who had a system of writing, although it seems there was no such system. I will assume the gentleman making this claim is aware that the Incas were very accomplished builders although they had no writing, but communicated through knotted rope, and either does not believe it or thinks their construction skills were not all they've been made out to be.
It's difficult to find anything about these ruins written by actual archaeologists on the Internet, although those who favor the alien explanation abound, but suffice it to say that when you encounter their writing claims regarding the age and construction of the site are much more tempered.
What is it that makes people see such ruins and think the only explanation for them is alien intervention? I think this results at least in part from the fact that we cannot be sure just how and why they were made, as they were made long ago and no records were kept. We don't often encounter people who maintain that the ancient Greeks or Romans were beneficiaries of well-meaning alien super-intelligences, although their achievements were remarkable, because we have records regarding their construction. But in the absence of any clear evidence that will actually resolve the question many of us tend to stop thinking and start--dreaming.