Descartes ontology, which serves as the basis to this school, will be considered in due course, and its error exposed. But partial, or subjective, knowledge cannot be the basis for any rigorous study, and therefore epistemology in inherently problematic. Indeed the historical verdict is that epistemology only leads towards resolution when knowledge is taken to be the basis for action, or in other words, when knowledge becomes the substrate to morality. When not leading to morality, epistemology inevitably leads to the doors of skepticism. The skeptical end is always apparent in the epistemological tradition.
Heraclitus, in the sixth century BC declared that nothing can be known, and the reason stated is that all things are in a state of flux. One cannot step into the same river twice, he is reported to have said (Russell 1945, p. 48). That which is true must be true at all times, and therefore cannot be subject to change. If the knowledge of man is always subject to change, the knowledge is then put into a state of doubt, and therefore it leads to skepticism. It must be pointed out that Heraclitus does not say that nothing is true, only that nothing can be known. Parmenides expresses the same thing in a different manner.
His claim is that nothing changes (Ibid). Truth itself implies immutability. That which is true necessarily exists, and therefore existence is itself immutable, from which Parmenides conclusion follows. The claims of Heraclitus and Parmenides may be said to be the two sides of the same coin. One expresses the inability of man to come to truth; the other that truth is all that exists, and that the mutable concepts of man are not part of it. This is an early demonstration of epistemology leading to contradictory claims, and therefore illustrates its problematic nature.
In ancient Greece we find three responses to skepticism. First there are the outright skeptics, like Zeno of Citium, Diogenes and Carneades, each giving rise to dedicated schools of skepticism. The common strand in such schools is resignation to fate and the abandonment of thought. The second response is that of the Sophists, who may be compared to the Utilitarians of the modern age. The Sophists were dedicated skeptics, but contended that thinking cannot be abandoned, being a natural part of the make up of man. Instead they channeled thought towards utilitarian ends.
For handsome fees they taught logic, rhetoric and the philosophical tools to all who thought they could use these. Indeed they actively promoted the practical uses of learning. Argument was valuable, not because it led to knowledge, but because it has the power to convince. And if one is able to convince, it becomes a tool towards advancement in public life. The reaction against the Sophists was led by Socrates, and his is an example of the third kind of response to skepticism. Truth may be beyond grasp, but it is the duty of man to pursue it nevertheless, he taught.
Socrates persisted in asking fundamental questions, to the bafflement of his listeners because he seemed unable to come to conclusive answers. He would ask questions like What is truth? , and would engage in lengthy discussions on the theme with prominent citizens of Athens. His disputants learnt many things on the way, but felt dissatisfied in the end because the original question was left unanswered. Socrates confessed plainly that he did not have the answer to the question, and in his ignorance he kept on pursuing it, because such a question is of the highest importance.
It has come to be known as the Socratic method of investigation (Brickhouse and Smith 1994, p. 3). It is characterized by two aspects. First there is the acknowledgment of truth. And second there is the duty to pursue it, despite there being no immediate answer. Therefore, resolution is only through the imposition of morality, which in this case is the duty to pursue knowledge. The Sophists promoted immorality, and this is not the path to truth, says Socrates. Only the moral response is adequate, and is the only way in which skepticism can be evaded. This is a theme that can be shown to repeat itself in all epistemological endeavors.