When we know something, or at least think so, do we really know it then? Can it be that we on some occasions know a thing and on other occasions we do not know it, even though we haven’t forgotten it and can tell exactly what it is that we are supposed to know? When browsing on the Internet, I found this interesting case by Keith DeRose, which I quote from Nestor Ángel Pinillos “Some Recent Work in Experimental Epistemology” (Philosophy Compass 6/10 (2011): 679):
 My wife and I are driving home on a Friday afternoon. We plan to stop at the bank on the way home to deposit our paychecks. But as we drive past the bank, we notice that the lines inside are very long, as they often are on Friday afternoons. Although we generally like to deposit our paychecks as soon as possible, it is not especially important in this case that they be deposited right away, so I suggest that we drive straight home and deposit our paychecks on Saturday morning. My wife says, “Maybe the bank won’t be open tomorrow. Lots of banks are closed on Saturdays.” I reply, “No, I know it’ll be open. I was just there two weeks ago on Saturday. It’s open until noon.”
 My wife and I drive past the bank on a Friday afternoon, as in , and notice the long lines. I again suggest that we deposit our paychecks on Saturday morning, explaining that I was at the bank on Saturday morning only two weeks ago and discovered that it was open until noon. But in this case, we have just written a very large and very important check. If our paychecks are not deposited into our checking account before Monday morning, the important check we wrote will bounce, leaving us in a very bad situation. And, of course, the bank is not open on Sunday. My wife reminds me of these facts. She then says, “Banks do change their hours. Do you know the bank will be open tomorrow?” Remaining as confident as I was before that the bank will be open then, still, I reply, “Well, no. I’d better go in and make sure.”
The first case is clear: I know that the bank is open on Saturday morning and I behave like that. But how about the second case? If I am sure and know that the bank is open on Saturday morning, there is no need to check it. However, although I am confident to know it, nevertheless I check it. But there can be only reason to check whether the bank is open, if I do not know it or when I am not sure enough about it so that I can say “I know it”. Pinillos discusses then two possibilities: either knowledge is dependent on the context or, although knowledge as such is true, it is sensitive to stakes, i.e. “the idea that whether an agent who believes P also knows P may depend on the practical costs (for that agent) of being wrong about P: when the stakes are high, the epistemic standards for attaining knowledge may be higher.”(676) Pinillos rejects the first possibility. However, I think that there is at least one other possibility, namely that there are degrees of knowledge, an alternative that Pinillos does not discuss. Also then, just as Pinillos says, whether we are going to check our knowledge depends on what the consequences are when we are wrong. But we don’t check when we are for 100% sure. If that were so, we should have to continue checking and checking after each check, for the consequences in case we are wrong haven’t changed after each check. So why would we stop checking? But after the first one our knowledge has increased and we feel sure and that’s why we stop and say: we know it.