When is it better not to know, rather than to know, something? Given that knowledge is often held to have intrinsic value or to be intrinsically good (take the well-known aphorism that “knowledge is power,” for example), can there be cases in which it is better not to know, rather than to know, something?
Perhaps in some cases it is better not to know something, if there is nothing to be gained (or lost) by knowing (or not knowing) that thing. Unless one holds that all knowledge is intrinsically valuable and that there is always something to be gained by knowing something, then there may be cases in which one doesn’t lose anything by not knowing something. Indeed, there may be cases in which one loses something merely by attempting to know about something, if that thing is useless, pointless, and of no value to know about. There may be cases in which it is better not to know about something that is irrelevant to one’s particular field of (moral, scientific, professional, social, or intellectual) inquiry, if that thing is potentially distracting or misleading.
It may also be better in some cases not to know about something, if knowing about it will lead one to expend unnecessary efforts or submit to unnecessary interventions that will ultimately be detrimental or of no benefit. Thus, for example, submitting to medical tests in order to diagnose whether one has cancer may in some cases be needlessly burdensome and medically unnecessary, if knowing that one has cancer and having it treated will not produce any benefit with regard to one's life expectancy or quality of life.
It may be better in some cases not to know about something, if knowing about that thing will be harmful or detrimental to the knower. Unless a person has a moral right to know about something, regardless of the fact that such knowledge may be harmful to that person, or unless a person has a moral responsibility to know about something, or unless the well-being of others depends on a person’s knowing about something, then there may be cases in which it may be better for that person not to know about that thing. If only harm, and no good, can come from a person’s knowing about something, then it may be better for that person not to know about that thing (although there may be a serious question as to who has the moral right to decide what knowledge about a given thing will be harmful, and to whom such knowledge will be harmful).
Who has the moral right to decide for another person that it is better for him or her (or that it is in his or her best interest) not to know something? Must this right (if there is such a right) be reserved solely for a parent, family member, or legal guardian? How about a friend or advisor? An attorney? An elected public official? Does a government ever have a right to decide that it is better for a society not to know about something?
Whoever decides that it is better for someone not to know about something may be exercising a form of censorship or paternalism with regard to knowledge about that thing. Judgments may therefore need to be made about whether such censorship or paternalism is justified or unjustified, necessary or unnecessary (and in what context it may be justified or unjustified, necessary or unnecessary).
There may be cases in which it is better not to know something, if one is emotionally or psychologically unprepared to deal with the possible consequences of knowing that thing. Discovery of unknown or unsuspected facts, occurrences, or events may in some cases have unanticipated consequences for the emotional and psychological well-being of the discoverer.
It may perhaps be better not to know something, if such knowledge will cause an unnecessary and unwarranted change in the attitudes and behavior of the knower. If knowing about something will have a significant adverse effect on the attitudes and behavior of the knower, even though the thing is actually of little significance, then knowing about it may be detrimental to the well-being of the knower (as well as to the well-being of those in his/her family, social group, or community).
There may be cases in which it is better not to have known something than to have known it and have acted without proper attention to, and regard for, its significance.
It may perhaps be better not to know about something, if one will be held morally or legally culpable for knowing about it. At the same time, however, one’s moral or legal culpability (or lack of it) for knowing about something may depend on whether one has wrongfully gained that knowledge or whether one has wrongfully acted or failed to act upon that knowledge (even if one has not wrongfully gained that knowledge). Similarly, one's culpability for not knowing about something, if one has been expected by others to have known about it, may depend on whether one has wrongfully failed to know about it or whether one has merely innocently failed to know about it through no fault of one’s own.
It may be better not to know something, if knowing that thing will lead one to have false hopes, expectations, or preconceptions about that thing. Knowing something may in some cases lead to frustration, disappointment, or denial if one’s hopes, expectations, or preconceptions about that thing are not fulfilled.
It may perhaps also be better not to know about something, if one knows that one does not know, and that unknown thing (entity, fact, event, etc.) turns out to be relatively unimportant, but investigating it leads to the discovery of other things (entities, facts, events, etc.) that are much more important and that one would not have discovered, had one not known that one did not know about that thing. Another way of saying this is: it may be better not to know about something, if knowing that one does not know produces much greater knowledge than would otherwise have been attained.