The idea of metaphysics is a complex idea that focuses on expanding beyond the mere realities of physics within the natural world. In a sense, this goes "beyond physics," in that the study of metaphysics is "devoted to matters that transcend the mundane concerns" expounded by those of practical scientists such as Einstein and Heisenberg (van Inwagen, Peter). So in a broad term, "metaphysics" attempts to delve deeply into the matters that try to understand and explain that with which still has no explanation.
Neither Plato nor Aristotle coined the term "metaphysics," though it does become the name of Aristotle's collective works, which revolved around the subject that would be later known as "metaphysics" (or "ontology"). In attempting to answer the metaphysical questions of "What is Substance?" And "What is there?" both Plato and Aristotle provide ideas that could help them understand these questions. In some respects, both philosophers attempt to discuss the "essence" of a particular subject; while Plato says nothing about a thing having a particular nature, Aristotle argues otherwise. Into the enquiries of a particular likeness and unlikeness of a particular subject, Plato attempts a resolution by impinging on the notion of "opposites." In Plato's explanation, opposites of the Form cannot be copresent within the same subject, ergo "it is only when the opposite is the subject that the restriction is operative" (Scaltsas, Theodore). On the other hand, Aristotle takes the same subject and imbues upon it numerous natures. Aristotle does not rely on the Form idea like his old teacher, but rather builds upon this idea and creates Categories, which introduces the variable of secondary substances and primary substances. In this, Aristotle "departs from Plato by introducing [the] distinction between the nature of a thing and its features" (Scaltsas, Theodore).
The subject of epistemology is related much to metaphysics in that it is the nature of which one gains knowledge of matters beyond the physical world. That is, epistemology is the idea of gaining the knowledge, whereas metaphysics is the idea of the knowledge and understanding which has been gained. Plato and Aristotle have greatly differing views on the subject matter; in fact, it can be said that Plato and Aristotle stand on the opposite sides of the spectrum regarding their philosophies on knowledge. Plato argues for a priori rationalism (Kreis, Steven); that is, he believes that the knowledge is inherent within a being, and thus experience is not necessary in gaining understanding of an idea. Aristotle, however, disagrees on this ground, and argues for a posteriori empiricism (Kreis, Steven); that is, he believes that knowledge is only gained after the experience of an event.
Where metaphysics is concerned, Plato argues that knowledge is there, that Forms are the "basic objects of knowledge, and Forms are not in the physical world, [therefore] knowledge must have been acquired at some point prior to [a being's] commerce with the world" (Silverman, Allan). Aristotle, however, argues toward the idea of causality; without cause, there is no effect, and without effect, there is no knowledge gained through experience. Aristotle believes that transient beings gain "knowledge of a thing only when [they] have grasped its cause" (Falcon, Andrea). This all boils down to the idea of Forms and Absolutes; the subjects become the major matters regarding the epistemology of both Plato and Aristotle's metaphysical philosophies.
The human condition and the belief of the transient being is perhaps the sole reason why philosophers undergo to further understand their thinking capacities. Humans think, and, as Descartes so perfectly put it, "I think therefore I am." Descartes, however, was not the only philosopher to put forth and ponder the mind-body problem. Are mental experiences related to physical experiences, and if not, why? Plato and Aristotle further expand on this problem by introducing the spirit -- or the soul -- into the equation. Of course, neither views the essence of the soul -- or the ethics and happiness of a being -- in quite the same manner.
Plato's parable of the cave gives a great insight into his ideas of the human being and the human being's soul: "[The] cave is the region accessible to sight or perception; the world outside and above the cave is the intelligible region accessible not to perception but to reasoning; the upward journey out of the cave into daylight is the soul's ascent to the intelligible realm" (Losin, Peter). Plato's belief of a human's well-being is not happiness per se; instead, he states that the soul remains steadfastly apart from the body and its pleasures (Frede, Dorothea). Happiness is not the means to an end, but the end after the attaining of perfection. A healthy soul is a perfect one, which in turn is a happy one. Aristotle, on the other hand, divides the soul by numerous virtues, and the unification of such virtues makes the soul one. For Aristotle, the human soul is divided into three sections: the nutritive -- "[the one] concerned with growth"; the digestive and reproductive -- "[the] appetitive part concerned with sense-perception, appetites, and the emotions"; and the rational -- "[the] one devoted to practical thinking," and "theoretical thinking such as mathematics and astronomy" (Gottlieb, Paula). By attaining a certain harmony between these three souls, a human being's ascendance out of Plato's cave can be carried out in harmony.
4. Political Philosophy
In accordance to Plato's belief in how a human being's characterized, Plato views the philosopher as the ideal ruler for his government. In his Republic, Plato suggests that there is no democracy more appealing than a non-democracy; that the "citizens are the least desirable participants in government" and that the "philosopher-king [should] hold [the] reins of power" (Kreis, Steven). Plato sees the community working along three different denominations: workers, soldiers, and philosophers. It is in the nature of the worker to love material goods, in the nature of the soldier to love honor, and in the nature of the philosopher to love wisdom (Frede, Dorothea). Should these three denominations work to bring their loves to a completion, then it is an ideal community. At the head of this is the philosopher-king, the most knowledgeable in political matters.
Aristotle does not view Plato's political theories as ideal. To be sure, Aristotle does "frequently [compare] the politician to a craftsman," wherein he "explains the production of an artifact in terms of four causes: material, formal, efficient, and final" (Miller, Fred). However, unlike Plato's limited characterization, Aristotle sees the city-state's community as made up of individual citizens. The citizens and the resources given within the environment -- or within the citizen's natures -- are the building blocks of a fashioned city-state. Yes, a community does hold in itself a ruling class -- or an authority figure, as it were -- but this is not limited to a philosopher-king. To Aristotle, the leader of such a varied community should be elected as "defined by the constitution, which sets criteria for political offices" (Miller, Fred).
5. Philosophical Backgrounds
It is highly interesting to note that Plato and Aristotle are perhaps the most influential -- if not the most influential -- philosophical figures in the ancient world. It is also interesting to note that Aristotle studied under the tutelage of Plato, and before that, Plato studied under the tutelage of Socrates. So it is surprising to see how the two figures find such different ways of viewing metaphysics and the ideas behind the thinking being. Plato sought to marry his teachers' ideas, finding resolutions to Socrates' and Heraclitus' metaphysical problems. Aristotle maintained the belief that his predecessors had only grasped at the fundamentals of metaphysics; that there needs to be further delving into such knowledge. Socrates wrote nothing, which Plato remedied. Aristotle wrote to debunk his teachers' ideas. And thus…