Epistemology is the theory of knowledge. It attempts to answer such questions as: How does one acquire one's knowledge? What is knowledge? What is possible for us to truly know? Epistemological inquiry also deals with skepticism regarding certain claims of the true nature of knowledge. Ontology is the science of being. Ontological inquiry attempts to answer the fundamental questions of existence, and thus is the central subject of metaphysics in philosophy. Some of the basic questions of ontology include: What is existence? What is an object? What constitutes the identity of an object?
Our textual sources for Socrates' thought come mainly from Plato. Plato was a direct student of Socrates, and was the only student to write down all of the philosopher's principle teachings. Aristotle refers to Socrates in passing in his philosophy, but does not idealize him in the same way Plato does. Another student of Socrates, Xenophon, also authored a number of Socratic dialogues.
Socrates was described by Plato as "atopos," meaning he was out of place. The fact that he was an intellectual means that he did not fit in with the prevailing standards of conduct in society - he was different, an outsider. In his philosophy, Socrates utilized what is now known as the Socratic method of "elenchus." This is a dialectical method of inquiry in which a speaker puts forth certain ideas, and the respondent agrees to some of these ideas while disagreeing with others.
According to Socrates, the philosopher is the wisest of all men because he is the only man who knows that he knows nothing.
Socrates identified evil with ignorance. On the other end of this spectrum, he identified goodness with knowledge. Thus, one only commits evil when one does not have the illumination of knowledge to fall back on. In the absence of knowledge, one cannot commit evil willingly; they may only commit evil when they are unaware they are committing evil. From this point-of-view, there can be no weakness of will.
For Socrates, a satisfactory definition had four components. A definition must be objective. Secondly, a definition must be fundamental for knowledge. Thirdly, a definition must be fundamental for morality. Finally, a definition must be of a thing, rather than a word. So, for instance, "justice" is not merely a word; a correct definition of "justice" would explain, from an objective, rather than personal, viewpoint, what the nature of justice is. This definition must be morally accurate and add to our general knowledge.
In Syracuse, Plato attempted to put his ideas about the potential role of philosopher in human society to test by becoming the advisor of Dionysus II, the ruler of Syracuse. Plato did not find the situation to be conducive to the practice of philosophy, however. He eventually gave up after Syracuse entered into war and returned to Athens.
Plato's attitude towards writing philosophy was highly ambivalent. He felt that, by teaching men to rely on writing and literature, then they will rely on what is written and cease to have the ability to exercise memory of what they have been taught. Thus, writing should be treated as a tool for reminding people of what they have been taught - but not as a replacement for memory, which is of supreme importance.
The story of Gyges's ring occurs in The Republic in order to examine the nature of justice in fuller detail. It is rooted in the legend of Gyges, who was alleged to have discovered a ring that made him invisible. Thus, he was able to do whatever he wanted without suffering any consequences. He could break into the royal court, seduce the queen, kill the king, and take over the entire kingdom unobserved. It is argued, in The Republic, by Glaucon, that an unjust man would do the same thing, were he given the opportunity. He thus argues that the only reason why people behave in a just fashion is because they are afraid of being punished for unjust actions.
Plato believed that the ideal city would consist of three classes of individuals - rulers, soldiers, and people. Those in the higher classes should be people who have special skills, although Plato acknowledged the fact that the descendants of these individuals would occupy the upper classes in the future.
Justice is ultimately defined by Plato as doing what one does best within the class system of the city as designated in question 10 above. In a just society, the organization of the city corresponds to the tri-partite organization of the human soul. Thus, each of the three classes corresponds to a different part of the soul.
Meno's paradox arises in a dialogue between Socrates and Meno on the nature of virtue and whether virtue can be taught. Socrates claims that this issue cannot be resolved. Meno then asks Socrates how one can search for virtue when one does not know what virtue is. And if one does run into an instance of virtue, how does one know that this is the thing he has been searching for? Socrates resolves this paradox through his theory of recollection. He comes to agree that inquiry is, in fact, possible. When we appear to be learning something new, what we are actually doing is recollecting something that we already know.
Plato's theory of forms has it that the material world as it appears to us through our sense is not actually the real world. Rather, it is a shadow of the real world. This helped Plato solve the problem of universals. The impressions of the material world come to us through our senses, while the forms of this world are then processed in our mind as ideas. So, for instance, there are many different chairs in the world. But the idea - the form - of chairness is what is at the core of all these chairs - what thus unites them in to one universal category.
The imperfection argument in Plato's Phaedo serves two purposes. It is first of all an argument in defense of the existence of forms. Secondly, it argues in favor of our possession of a priori knowledge. This is rooted in the imperfection of sensible objects. It also relates to our ability to make judgments about those objects.
In The Republic, Socrates inverts what is commonly believed to be knowable and what is real. Just because you can grasp something in your hands does not necessarily mean that it is real. In opposition to the common man, Socrates posits a view of knowledge in which what one perceives through one's senses is not necessarily real.
For Plato, physics is impossible as a science because he believes that ideas in phenomena are less real than ideas in the human world. As physics is the knowledge of the ideas in phenomena, it is not significant when compared to ethics and the sort of dialectical inquiry pioneered by Socrates.
The reason why we know that certain things exist and are knowable is because they are illuminated by the sun. In the cave (see below), the cave is meant to represent becoming, while the fire in the cave that provides illumination is meant to represent the sun up above.
If a man has lived in a cave all his life, chained up as a prisoner, all he has seen are shadows on the walls. He believes that those shadows are real phenomena. Then one day, he is released out into the real world. The shapes that pass by him will seem less real than the shadows he spent his whole life watching. The last thing the prisoner would see is the sun, which provides all illumination for these objects and presides over all things he is able to see. The sun is thus the cause of the prisoner's being able to see all these things. Having been enlightened in this fashion, the prisoner would not want to return to the cave to free his fellow prisoners, but would feel compelled to do so. The prisoner's eyes would then have to adjust to the darkness of the cave once again. He would thus have to return to his previous way of seeing. Having been taken to the surface, his eyesight would have been nearly completely ruined.
According to Aristotle, the universe consists of five elements - earth, fire, air, water, and aether. The first four of these are earthly elements. Aether is that thing that makes up heavenly bodies and the stars and the heavens.
Aristotle held that of all things that exist, they could be divided up in to four categories of subjects and predicates. In the first category are those things that can be predicated of a subject, but are not contained in a subject. An example of this is man, which is predicated in the names of John or Jack, but it not contained in any particular subject. In the second category are those things that are contained in a…