All belief and all practice rested on law, and law was the result of a convention made among men and ultimately produced by individual conviction. What one man had done another could undo. Religious tradition and natural right, the sole external standards, had already disappeared. There remained the test of self-consistency, and against this all the subtlety of the new dialectic was turned. The triumph of Eristic was to show that a speaker had contradicted himself, no matter how his statements might be worded. Moreover, now that reference to an objective reality was disallowed, words were put in the place of things and treated like concrete realities. The next step was to tear them out of the grammatical construction, where alone they possessed any truth or meaning, each being simultaneously credited with all the uses which at any time it might be made to fulfil. For example, if a man knew one thing he knew all, for he had knowledge, and knowledge is of everything knowable. Much that seems to us tedious or superfluous in Aristotle’s expositions was intended as a safeguard against this endless cavilling. Finally, negation itself was eliminated along with the possibility of falsehood and contradiction. For it was argued that ‘nothing’ had no existence and could not be an object of thought.[71] VI. From utter confusion to extreme nihilism there was but a single step. This step was taken by Gorgias, the Sicilian rhetorician, who held the same relation towards western Hellas and the Eleatic school as that which Protagoras held towards eastern Hellas and the philosophy of Heracleitus. He, like his eminent contemporary, was opposed to the thinkers whom, borrowing a useful term from the nomenclature of the last century, we may call the Greek physiocrats. To confute them, he wrote a book with the significant title, _On Nature or Nothing_: maintaining, first, that nothing exists; secondly, that if anything exists, we cannot know it; thirdly, that if we know it, there is no possibility of communicating our knowledge to others. The first thesis was established by pushing the Eleatic arguments against movement and change a little further; the second by showing that thought and existence are different, or else everything that is thought of would exist; the third by establishing a similar incommensurability between words and sensations. Grote has attempted to show that Gorgias was only arguing against the existence of a noumenon underlying phenomena, such as all idealists deny. Zeller has, however, convincingly proved that Gorgias, in common with every other thinker before Plato, was ignorant of this distinction;[72] and we may add that it would leave the second and third theses absolutely unimpaired. We must take the whole together as constituting a declaration of war against science, an assertion, in still stronger language, of the agnosticism taught by Protagoras. The truth is, that a Greek controversialist generally