Good", which he called "Reason", "God", "Mind", "Wisdom", etc. This was the true essence of being, and was eternal and unchangeable. The idea of a universal good also allowed Euclid to dismiss all that is not good because he claimed that good covered all things on Earth with its many names. Euclid adopted the Socratic idea that knowledge is virtue and that the only way to understand the never-changing world is through the study of philosophy. Euclid taught that virtues themselves, however, were simply the knowledge of the one good, or Being. As he said, "The Good is One, but we can call it by several names, sometimes as wisdom, sometimes as God, sometimes as Reason", and he declared, "the opposite of Good does not exist". Euclid was also interested in concepts and dilemmas of logic. Euclid and his Megarian followers used dialogue and the eristic method to defend their ideas. The eristic method allowed them to prove their ideas by disproving those of the one they were arguing with and therefore indirectly proving one's own point (see reductio ad absurdum). When attacking a demonstration, it was not the premises assumed but the conclusions that he attacked, which presumably means that he tried to refute his opponents by drawing absurd consequences from their conclusions. He also rejected argument from analogy. His doctrinal heirs, the Stoic logicians, inaugurated the most important school of logic in antiquity other than Aristotle's peripatetics. See also List of speakers in Plato's dialogues Sorites paradox References Footnotes Citations Works cited Further reading — republished, on the internet, by the Jacques Maritain Center, University of Notre Dame, 11 November 2008. External links 4th-century BC Greek people 4th-century BC philosophers Ancient Greek educators Ancient Greek ethicists Ancient Megarians Megarian philosophers Metic philosophers in Classical Athens Pupils of Socrates Year of birth unknown Year of death unknown