“Man is the measure of all things." So spoke Protagoras in the fifth century B.C. Who was this man, and what did he mean by this “dark saying,” as Plato described it? We might consider Protagoras the father of the Sophists in early Greek philosophy. This group of thinkers arose because of skepticism toward the cosmologies postulated by previous philosophers of the Ionian School. There seemed to be no resolution to the conflicting views that emerged from the Ionian quest for the ultimate principles of nature. Consequently, the Sophists turned their attention from speculation upon the cosmos to the study of the speculator, that is, man himself.

This more practical interest in human affairs led the Sophists to a closer observation of differing cultures and civilizations and the corollary study of political life. What they observed were variations in moral codes and civil laws among people as groups and individuals. These observations in themselves were harmless enough, but the Sophists went one step further, arguing that this diversity existed because moral codes and civil laws were merely matters of human contrivance and convention rather than matters of nature or divine sanction as was the common understanding of their age.

Protagoras, in concert with his Sophist colleagues, avoided speculation upon ultimate principles and instead promoted a principle of moral relativism, arguing that “whatever practices seem right and laudable for any particular state are so, for that state, so long as it holds them” (Plato, Theaetetus, 166 c). Furthermore, Protagoras advocated an individual intellectual relativism as well, a notion reflected in his “dark saying” that "man is the measure of all things." 

For Protagoras, human perception and knowledge were identical. Frederick Copleston aptly summarizes the view of Protagoras as “what appears to you to be true is true for you, and what appears to me to be true is true for me” (Copleston, A History of Philosophy, Volume 1: Greece and Rome, 88). Therefore, each person’s belief, thought, or perception is equally as true as that of anyone else. Truth is not objective, that is, it is not "out there" somewhere waiting to be discovered. Truth is subjective, the internal possession of each individual, and hence there can be no knowledge of a thing in itself. 
 
Does all of this sound as strangely familiar to you as it does to me? “There is nothing new under the sun” (Eccl 1:9). If Protagoras walked our streets today, he would fit right in with our morally relativistic and intellectually and religiously pluralistic world, a world in which suggesting the existence of absolute truth may raise eyebrows or even provoke hostility. Protagoras might also be comfortable occupying the pulpit of any of a number of local churches that have become increasingly accommodating to postmodern thought and the moral and intellectual relativism that it spawns.

Many of these churches, like our culture, emphasize the practical and the “missional” at the expense of ultimate moral principles, objective knowledge, and absolute truth. It may come as a surprise, but the dangers of this view to the viability of rational inquiry and the possibility of common public knowledge were very apparent to the great Greek philosopher Plato 2400 years ago, and he confronted Protagoras’ position in his writings. In our next entry, we will examine how Plato dismantles the "dark saying" of Protagoras and how we may apply his argument in our contemporary context.