Understanding is a tricky thing to get a grip on via intuitions, partly because we philosophers haven’t spent several hundred years carving it up into philosophically digestible bites yet. But having said that, my intuitions about understanding diverge radically from my intuitions about knowledge. When I evaluate cases of putative knowledge, I want to know how easily S could have been wrong about p. I want to know whether S has the *right* to be sure about p. Just how careful was S in coming to believe p? All this has to do with how good a claim S has to having arrived at this particular truth.
But when I evaluate whether someone has understanding, my questions are very different. I want to know how well S grasps the interconnection among the different elements of the domain of her understanding, whether S gets the “big picture,” (please continue to add for yourself vague metaphorical characterizations of understanding, offered in lieu of an actual account of it…) In some cases, (understanding my car’s engine) I want to know if S can predict what will happen to one part of the system if it is perturbed in a certian way in another part. When it comes to understanding other people, I want to know if S is good at figuring out what so-and-so will do under such-and-such conditions. While such predictions don’t constitute understanding, they are good indications that it’s present.
But what’s noteworthy here is that I don’t ask questions about *how* S came to have the grasp of the big picture, the ability to predict others’ behavior, or whatever. I might be skeptical that someone has understanding because I think they’re simply *wrong*, and I might take as evidence for that their lack of justification for some of the claims that constitute their understanding, but I would say that in such a case, it is the presumed falsehood (or inaccuracy) of the person’s putative understanding that disqualifies it, not the related fact that the claim also fails to count as knowledge.
These remarks presuppose some organizational matters about the fundamental form of understanding, and treats the “subject matter” form as primary, and on that point, I’m in agreement with Wayne. What is interesting about Wayne’s comments is the difference in thought patterns cited between considering a putative case of knowledge versus a putative case of understanding. It would be interesting to see to what extent others see things the same way.
The other interesting point that is not often appreciated is the way in which any attempt to mine intuitions about understanding gets corrupted from two different directions. Intuitions about knowledge are likely to creep in when thinking about putative cases of understanding, and intuitions about explanatory adequacy as well. Wayne cites the point about intrusion by our intutions about knowledge, but it is equally possible for our intuitions about explanation to creep in as well, especially when we focus on the language of understanding why.