What Does It Mean to "Know" Something?

We have now had our last meeting of this semester's "Introduction to Philosophy" class. One of the units focused on epistemology. The main questions that animate epistemology are "What can I truly know (as opposed to merely believe)?" and "What are the limits of human knowledge?"

Descartes: "Cogito ergo sum."

To illustrate just how many ways there might be to understand "knowledge," and to have a bit of fun in the process, I gave my students the following list of things one might mean when one says, "I know x":


1. I have justified, true belief about x.


2. I (usually, sometimes, occasionally) act as if x is true.


3. I would be willing to bet on x.


4. People I trust believe x.


5. People I do not like believe not-x.

6. I am pretty sure (sufficiently convinced) that x is true.

7. I actually have no idea; the phrase "I know" is simply something people say to facilitate social interactions.

8. I have heard lots of people say x (say things that assume, are consistent with, x).

9. My friends (apparently) believe x.

10. I would look like a fool if I disputed x (cool, important, moral, or "in" people believe x).

11. Proclaiming that I believe x raises my status/allows me to flaunt (cheerlead for) my moral superiority/signals that I am in the "in crowd."

12. It would not occur to me to doubt x.

13. I have believed x for a long time.

14. I am willing to agree to x for the sake of argument.

15. I am tired of discussing this topic (with you) so I say "I know" in an effort to bring our discussion to an end.

16. I pretend it is true because doing so is important to me for other reasons (makes me feel good about myself, leads to (political, moral, social) consequences I desire).

17. It just occurred to me.

18. You just said you know it, and you are very persuasive.

What would you add to the list?