universalist dilemma
If one believes a certain proposition to be true for all times and for all places, the proposition can be said to be universally true. Conversely, if a proposition is only true for a particular time and place, the proposition may be true for other times and other places, but not necessarily so.
Consider the proposition that liberal democratic government is the absolute best form of government. This is a universalist proposition - that liberal democracy is the pinnacle of human political thought, that no other form of government, past or future, can surpass it in its ability to deliver on its promises of securing the right to life, liberty, and pursuit of happiness. Such a claim necessarily implies a hierarchy of values according to which all other forms of government ought to be judged and ranked based on their ability to preserve and uphold the aforementioned values.
From the universalist perspective, moral relativism is impossible. There are self-evident truths; some political theories are better than others at preserving these truths, therefore there must be one theory that is better than all the others.
But what if we modify our proposition: liberal democratic government is the best form of government for Englishmen. It might work for the Chinese or the Egyptians as well, but it also might not; in any case, it is none of our concern, as each nation may - indeed, must - decide for itself how it ought to be governed. This is the particularist formulation, and it is fundamentally incompatible with the universalist one.
For the universalist, self-evident truth claims which only hold for particular peoples in particular places are not truths at all. 2 + 2 = 4 is either true whether one is in England or in China, or it isn't true anywhere.