In an argument reminiscent of Protagoras’ claim that "man is the measure of all things", the philosopher often cited as the most prominent defender of postmodernism, Richard Rorty, contends that there doesn’t exist a "skyhook" which takes us out of our subjective conditions to reveal a reality existing independently of our own minds or of other human minds.  In other words, humans are incapable of attaining a "God’s eye standpoint" that reveals reality in itself. Rather, each person interprets reality in accordance with his own subjective condition.
The argument, presented in this form, does manifest an air of profound simplicity—the element from which it derives its persuasive quality. Yet, a deeper analysis reveals Rorty’s contention that "we can’t know objective truth," to be self-refuting. In claiming to know that one cannot know objective truth, he is essentially making a positive truth claim, namely, that it is objectively true that one cannot know objective truth. Thus, this "Protagorian" argument is self-contradictory—it unwittingly indicts itself.
Furthermore, one could argue that objective truth is knowable, and that this ability "to know" stems from our own experience of discovering, or stumbling upon truths which exist independently of our own created subjective conceptions of reality. These can consist of both truths regarding the physical world, such as "trees have leaves," mathematical truths such as "two plus two equal four," and moral truths such as "murder is wrong." All the foregoing examples share a common attribute, namely, that they hold independently of our subjective conceptions of them. That is, their reality is not dependent upon how we perceive them. If murder is considered a moral abomination solely by virtue of the fact that our subjective human consciousness dictates it, then it logically follows we could make it "good," by thinking about it. The same would hold with respect to the other indisputable truths noted. Thus, Rorty’s argument leads to absurdities.
In a manner similar to that of Antiphon, Rorty, in accordance with the post-modernist school of thought to which he belongs, emphasizes the social influence upon the individual and his beliefs. Truth, or what Rorty substitutes for it, is an intersubjective agreement among the members of a community.  That intersubjective agreement permits the members of the community to speak a common language and establish a commonly accepted reality. The end of inquiry, for Rorty, is not the discovery of absolute truth but the formulation of beliefs that further the solidarity of the community, or "to reduce objectivity to solidarity."  Consequently, in the event that a given community argues in favor of specific values, this is not due to the fact that these values are objectively true—we can’t know objective truth—but rather, because they serve to increase "solidarity" within the community. Truth, in essence, is reduced to a matter of utility, a means to an end.
I have to admit that, on many issues our society behaves in a "Rortian-Antiphonian" manner. Consider, for instance, the issue of the environment. One’s position on this issue apparently hinges more upon whether one is a member of a conservative or liberal community, than the facts per se. The same goes for other issues, such as whether one believes that President Clinton is guilty of a crime, or whether the claim of marijuana’s purported "medicinal uses" is not simply a covert attempt by the hippies to smoke pot with impunity.
Yet at the same time, this emphasis on "solidarity" leads to irreconcilable difficulties. Let’s assume, for instance, that a patient is suffering from a potentially fatal disease that is fully curable by antibiotics. In his society, such illnesses are thought to be best treated by a witch doctor’s incantations and potions. A doctor, from outside that society, encourages him to seek conventional medical treatment, but to do so would subsequently be inconsistent with the patient’s society. Would Rorty and the post-modernist Sophists truly argue that there is no objective truth to this issue? Would they argue that we favor the conventional treatment solely by virtue of our "solidarity" with a different community?
Finally, I would like to consider a third argument, this one by Gorgias, which also comes into play with respect to contemporary post-modernism. The argument usually takes the following form: The word "True" is a modifier that describes only sentences. Thus in the absence of human speech and language, truth doesn’t exist. Rorty explains:
To say that truth is not out there is simply to say that where there
are no sentences there is no truth, that sentences are elements of
human languages, and that human languages are human creations…
the world is out there, but descriptions of the world are not. Only
descriptions of the world can be true or false. The world on its own—
unaided by the describing activities of a human being—cannot. 
This argument, as sound is it may seem, commits the fallacy of confusing a necessary condition with a sufficient condition. Take, for instance, the following example: The word "exists" can only describe a sentient being, yet the mere fact of existence is not a sufficient condition for sentience. And even if we were to grant that only sentences can be true, it doesn’t then follow that a sentence alone is sufficient for truth.The idea that only sentences can be true by no means removes the need for some other nonlinguistic condition to render the sentence true. Furthermore, it is not sufficiently clear that a sentence is necessary for truth. Even if no language existed when dinosaurs did, we would still be within our epistemic rights in claiming that the statement "dinosaurs exist" would have been true had human language existed. Therefore, since there does exist a reality, both independent, and prior to human language, it follows that human language, in itself, is not required as a necessary condition for truth.
Finally, I would like to consider the relevance of time difference in respect to this particular philosophical movement. On the basis of the foregoing discussion, it should appear obvious to the reader that the three most powerful arguments in favor of the "Sophistry" of the Ancient Greeks, and the "post-modernism" of the 20th century have incurred little or no change with time.
Yet at the same time, it is important to note that although the arguments haven’t changed substantially, the response with which they have been received has shifted dramatically. Whereas, in ancient Greece, those associated with "sophistry" were considered a pernicious threat to society and the status quo, in stark contrast, Western 20th century society has greeted post-modernism (as a contemporary manifestation of sophistic philosophy) with open arms. "The Art of Deception," as it were, has ascended from the status of ill repute to its emergence as the reigning paradigm of much of liberal academia. This acceptance of post-modernism, into the hearts and minds of the intellectual elite, cuts to the heart of the irrationalism that is sweeping our universities. In his work, The Closing of the American Mind, Professor Allan Bloom observes that:
There is one thing a professor can be absolutely certain of: almost
every student entering the university believes, or says he believes,
that truth is relative…The students, of course, cannot defend their
opinion. It is something with which they have been indoctrinated. 
In our society today, and especially within our universities, it is generally accepted as an unquestionable axiom that truth is relative. "You have your truth, and I have mine." So the post-modernist blithely asserts.
Both the unfettered domination and the wide spread uncritical acceptance of post-modernism, I think, can be accounted for in terms of our presently heightened awareness of so-called cultural issues, and gender equality. Perhaps post-modernism has afforded us the luxury, or is in some way or another conducive to an atmosphere in which we can slowly but surely overcome our old, traditional, judgmental, rational, moralistic selves. If in fact, there is no objective truth "out there", and hence no objective standard on which to base judgement, on what basis could anyone claim that a certain lifestyle was immoral, that certain cultures were inferior, or that particular ideas were false? The answer is none. People or cultures couldn’t be judged to be immoral; ideas couldn’t be regarded as true or false, but simply different. This consequence lies, ostensibly, at the heart of the current seduction of the post-modernist sophistry that has befallen our era.