Mapping out all of the different kinds of rights is certainly fun in its own right, but for our purposes here, it is probably enough to see that there are at least three different senses of the word "right" that might be relevant.

First, when a person says everyone has a right to his own opinion, he might mean that everyone has a legal right to his own opinion. That would mean that by holding the opinion in question one is not violating a law or regulation, that society allows a certain latitude in the views that people hold, and that this opinion is still within the boundaries society has set.

Having a legal right to an opinion means that one should not be punished by society's legal system for holding that opinion, but there still could be other negative consequences for holding the opinion. Opining that all of your neighbors are out to get you, for example, is certainly legally allowable, but it may lead to a certain level of unpopularity at neighborhood block parties.

In terms of a legal right to hold our own opinions, we no doubt do have such a right.

We even have a fairly broad right to express our opinions, although that legal right is not as broad as it was before the Patriot Act.

A second meaning of "right" when people say, "Everyone has a right to his own opinion" is somewhat similar and yet noticeably different than the legal right. Some people seem to mean that people have a "social right" or an "acceptance right" to his opinion. (I'm just making up these terms. I don't know if there is a generally accepted terminology here.)

A social right, as I am calling it, would allow one to hold a view without having any negative consequences befall one for one's opinion from within a certain social group.

Let me compare that with a legal right to an opinion for a moment. We can see there is a difference among society, its rules, its preferences, and its means of enforcing its rules. The legal system is one of the strongest ways society has to enforce its rules. And if we have a legal right to an opinion, it means that society will not be using the legal system to force people to hold or to reject that opinion.

Now a social right occurs when society does not use other means -- not the legal system, but something like social acceptance or rejection -- as a way of forcing people to hold a certain opinion.

Maybe it is easier to see what I mean here by using an example of when one would seemingly not have a social right to one's opinion. In a meeting of the National Abortion Rights Action League, for example, one may not have the social right to have the opinion that abortion is murder. If one expressed that opinion, one could expect to be shunned or maybe verbally attacked for one's opinion. One would not be accepted by the social group. So even though you would have a right to your own opinion in the legal sense, you might not have a right to your opinion in that social sense of right.

Often, when people say something like "everyone has a right to her own opinion," they seem to be suggesting that they may disagree with the opinion, but they will accept the person who holds that opinion anyway. In fact, I would say this is the most frequent meaning of the "everyone has a right" claim.

But there is a third sense of saying "everyone has a right to her own opinion," a sense in which people frequently do not have such a right. We might call this a "knowledge right." You have a "knowledge right," in the way I intend to use the made-up term, when your opinion is well justified based on the evidence or other rational bases that you should have available to you.

So suppose that Sen. Hillary Clinton were to say, "Seven plus five equals 13," and suppose that to be her genuine belief or opinion. Should we simply say, "Well, everyone has a right to her own opinion"?

No, definitely not, at least if we mean it in the knowledge right sense. Even if Ms. Clinton feels deeply that seven plus five equals 13, even if we accept her into our social group despite her mathematical challenges, even if she does not even violate the Patriot Act by saying this (even when she is talking to someone outside the borders of the United States), given the mathematical truths that she should know, she has no right to believe this error.

She has no knowledge right, that is.

Too many of us are too nice to people. We are willing to extend social rights to almost any opinion.

But if people have no knowledge rights to some really bad opinions, then I am not sure they should have the social rights to those opinions either.

When people should know better, perhaps we should let them know.