Any man may make mistakes, wrote Cicero, but only the fool persists in error (or words to that effect). According to Wallace Stevens, "the mind is never satisfied, never." I think there are times when we persist in error because our minds are not satisfied, though they should be.
This seems to occur particularly when little but our minds are involved. I don't wish to propose the old mind-body dualism, as I doubt its veracity and question its usefulness. But I suggest that we err, repeatedly and for no good reason, most often when we are "only" thinking; when, in other words, we are not doing anything which requires active interaction with our environment (yes, the "real world" or worse yet the "external world" as some would have it).
When we err in the world, chances are good that we will be made aware of our error, sometimes forcefully. We will fail to resolve a problem, we will find ourselves checkmated or down a piece in chess, we will be sued (such fun!), we will be caught flat-footed by a riposte, we will be confronted by angry, aggrieved people, we will be involved in an accident. When we aren't engaged in the world, when we indulge ourselves in speculation which will have no consequence--which by its nature can have no consequence or perhaps more pertinently can make no difference--we can go on erring forever. And sometimes we do (well, I can't say forever, of course, as we continue; our time is not yet up, for good or ill).
I've wondered why we continue, in philosophy, to address certain questions which have been addressed for thousands of years. I am, of course, no philosopher (this will I'm certain be thought if not noted by any actual or would-be philosopher who chances upon this post). However, it seems to me as a mere dilettante that some philosophical questions purportedly addressing "knowledge" and "reality" never go away. They are unanswered in any fashion that satisfies. They are considered, again and again and again, by various and sundry century after century. There is a kind of relentlessness involved in this consideration. And few seem even to consider the possibility that the fact these questions are asked and answers given and rejected continually may be indicative of a problem with the questions, or the uselessness of the pursuit of their answers (there are indeed a few, a noble few I think, but too few).
The philosophers who've pondered these questions obviously are not fools. They don't persist in error in the sense that someone driving a car would by driving it into a tree again and again, or in the sense a fencer would by repeatedly running into the point of his opponent's weapon. What error, really, can they commit? An error in logic, perhaps. But when one claims we can't really know, for example, the true nature of a coconut, as we can only know its appearance, one can't hurl the coconut at them (much as we may want to) and demonstrate their error. They will merely claim that they were struck by what had the appearance of a coconut but the true nature of which cannot be determined.
Perhaps the mind is insatiable, like Messalina, most especially where there is nothing to be gained or lost by its use.