Paradoxes are useful because they help us assess the really interesting and relevant parts of our argument. Their existence typically drives development in the theory, allowing us to modify our current theory in order to remove such problems. With regards to the liars paradox, one solution is to think that our language can only be considered on different levels, and that a given sentence is only able to make truth valuations of sentences on a lower level. As a result it is not possible for the sentence to evaluate it's own truth. Other solutions we might be looking for are to reject the correspondence theory of truth in favour of a new theory.
On thing to note is that paradoxes typically apply only upon our intuitions and do not really exist in a formal sense, mathematical sense. This is because we typically require a mathematical system to be logically consistent. If it is not, then the paradox causes the Mathematical system to change. Perhaps the most famous example of this is Russells Paradox and it's impact on set theory. Suppose that we think everything is a set, and that there is an axiom that allows us to consider the set of all things that satisfy some property $\phi$. Thus we can consider the set $R = \{x : \neg ( x \in x)\}$, that is the set of things that do not belong to themselves. However, since we assume everything is a set, $R$ must also be a set and thus we can consider whether $R$ belongs to $R$. If we follow our logic, the system is necessarily inconsistent. At least in terms of set theory, our solution is to reject the axiom so that we are able to consider the set of all things that satisfy $\phi$. We are only able to consider the set of all thins that satisfy $\phi$ already considering a bounding set.
Now the paradox that I wanted to discuss today is the Paradox of intolerance. The paradox itself works as follows: it seems that a tolerant person is likely to antagonistic views with regards to intolerance. However this seems to imply that they are acting intolerantly to those that are intolerant, which itself appears intolerant.
Essentially what we are interested in is whether this is justified. At least according to the paradox it seems as if a tolerant agent should be tolerant to all other agents, regardless of their own tolerance. However intuitively it seems for various reasons, including self preservation, a tolerant agent has a degree of obligation to respond negatively to those that would express intolerance in a manner that causes harm to others. For it seems minimally plausible for someone to be tolerant but wish to prevent a Nazi from killing Jews.
How ought we respond to the paradox? Well the initial response is to consider tolerance as a bounded concept. One has a right to be intolerant towards those who are they themselves intolerant. However this seems a bit odd : what if the intolerant individual is not causing any harm or what if they barely expressing their intolerant views? Instead perhaps we should modify our theory such that we should only be intolerant to those whose intolerance would negatively affect others around them.
Now consider a slightly more difficult issue. According to our theory above, one is allowed to react intolerantly towards someone who is representing Nazi like views. Thus in this sense we might be allowed to limit their freedom of speech, and not allow them to express their beliefs. Let us call this situation A. Now consider a situation B where anyone who is acting intolerantly towards someone else who is expressing Nazi like beliefs can be silenced by a group one level higher. After all the people who are acting intolerantly with respect to others with Nazi like beliefs are they themselves negatively hurting those around them who are themselves expressing Nazi like beliefs. Whilst I think most peoples intuition is that situation B is wrong, the justification for why it is wrong is not particularly simple. I think most justifications hinge upon the notion that the group who are expressing Nazi like beliefs are inherently wrong, and thus it is fine to silence them. However it is not obvious why this is the case. We could at least imagine a possible world where a Nazi like belief is justified and where there is something fundamentally wrong with silencing them.
Note that in my above argument I think it is important to consider each belief and action separately. We can perhaps express moral values upon each statement, but these moral values do not hold in the modal sense. It is not necessarily necessary the case that certain actions are wrong. By this I mean that it possible that Nazi like views are actually necessarily wrong, but we don't know this yet, and thus for sake of our discussion of universal theories we should take this into account.
Anyway the problem here is that there are those who wish to espouse being tolerant of others views, but wish to justify intolerance in certain cases (notably to those who are already intolerant). I wish to say that there is a fundamental difficulty in assessing whether they are justified in being intolerant of others. Perhaps you think my example of a Nazi like belief is extreme. How about a religious view? If a religious person expresses beliefs that say I am going to go to hell (as a result of their religion, even if they are personally friendly to me), am I justified in being intolerant of them?
Further difficulties arise because a lot of our judgements about being intolerant of intolerance arise from somewhat utility based arguments; considering the total amount of suffering by allowing an intolerant view to be expressed. Yet many responses are they themselves irrational. Should we justify being intolerant to certain views that cause irrational reactions? How about it is revealed that a significant majority group of people get fundamentally offended each time anyone makes a feminist remark on the news. Should we silence people from making feminist views? Perhaps someone makes the argument that the feminist view is intolerant of those who wish to live in a status quo of a patriarchy. Does this provide me justification?
On final thing to reiterate is that the examples I've used here are simply that: examples. I don't necessarily endorse any of the views espoused here, I have simply chosen them because they seem to correspond to some intuitions. And yes, I have had to make a degree judgement here as to what view is intuitive and what is not. I think that's permissible.