Art
Throughout this dialogue, as well as in many of Plato's other works, the notion of artful pursuits comes up rather frequently. Essentially, an art is a skill directed towards some form of the good and intended for the benefit of those practicing and/or those on whom a particular art is practiced. In this sense for example, medicine is an art because it aims at improving the physical health of those for whom a specific treatment is prescribed, while serving alcohol is not as it creates a deceptive impression of physical health grounded in the bodily pleasure of intoxication
In Gorgias, Socrates first mentions the notion of art as part of an inquiry into the nature of rhetoric. In discussing this topic, he distinguishes between true arts (defined above) and false ones (routine/flattery) which create an incorrect impression of good by means of the pleasant (which Socrates later defines as different from—and less desirable than—the good).
This distinction becomes increasingly relevant as the dialogue progresses, since Socrates maintains that most of his contemporary Greeks and Athenians have been led astray from the path of virtue exactly because they mistake false routines of pleasure for true arts of good. Consequently, for Socrates's fellow citizens, the nature of politics, justice, power, good living and the like is based upon a fundamental conflation of true and false arts corresponding to a belief that the pleasant equals the good. The entire text considers how this confusion of art with flattery manifests itself, and as such it adds great strength to Plato's overall philosophical project of defining virtuous existence.
Power
The nature of power embodies a concept crucial both in Gorgias as well as to Plato's larger philosophical beliefs. For Socrates's contemporaries, the rampant view of power is as the ability to rule over others and to satisfy one's own desires. This position is best expressed by Polus (466–69) and Callicles (490–492).
Plato takes great care to debunk this formulation. On the one hand, Socrates argues, those who rule others often must perform actions they do not will in order to benefit the state of which they are in charge. In this sense then, apparently powerful tyrants are often unable to act as they will, and true power is shown to consist of something other than ruling over others. At the same time, those who repeatedly satisfy their desires do not possess real power because this gratification further fuels rather than extinguishes the appetites. A person capable of always satisfying desire is in constant need of more satisfaction, and as such possesses no true power. This point is illustrated in 493b by the metaphor of the leaky jar.
Instead, Socrates argues that true power comes with the control and order of one's body and soul—the discipline to act justly, live virtuously, and not need anything. This treatment of power becomes all the more significant in light of the events surrounding Socrates's actual trial and death. The philosopher was accused of corrupting through false instruction and treason, and convicted and executed because of his refusal to admit having acted wrongly. In light of this event and its close proximity to Gorgias' creation, then, the nature of power for Plato takes on crucial importance in that he must prove his teacher died in strength rather than weakness.
Evil
The question of evil comprises an important theme for Plato. Evil takes root in wrongful acts—those which by nature involve shame and/or pain. Not only is this position argued in Gorgias by Socrates, but the other participants in the conversation agree with him as well. This aspect of evil exists as one of the text's few uncontroversial claims.
Dissention enters instead with the discussion of what is the greatest evil, or which is "worse": to suffer or to inflict wrong (e.g. 473a). On the one hand, Socrates's opponents (mainly Polus and Callicles on this issue) state that suffering wrongdoing is worse, since it places the sufferer in a position of pain and subjugation to the inflictor. On the other, Socrates maintains that committing wrong is worse, since it is more shameful and therefore painful and evil. He goes on further to declare it worse still to inflict wrong without being punished, since retribution for an evil act at least helps to right the wrong.
Such considerations are integral to Plato's purpose within the dialogue, because wrong and evil relate directly to its other key topics: the inquiries of art, justice, politics, virtue, and temperance center around what is right and wrong conduct within each field of focus. The notion of evil also is important within the scheme of Plato's overall body of work. This is so at least in large part due to the death of his virtuous teacher at the hands of an apparently evil government. For Socrates not to have died in vain and supreme evil, nor to leave behind a legacy of error, such definitions of wrong must prove convincing. As a consequence of this fact alone (independent of his general and powerful interest in the philosophical character of right and wrong), the nature of evil constitutes a recurring theme of Plato's philosophy.
Temperance
Though Socrates's discussion of temperance in Gorgias initially appears rather specific and therefore of limited impact, its key role in the attainment of virtue quickly renders its impact far-reaching. Temperance (separate from its application) signifies a certain quality of self-control and discipline. In this sense, it is a fairly simple and non-contentious concept.
Socrates goes on, however, to define such integral notions as power, justice, and proper living (among others) to a large degree by reference to temperance. In this way, individual power lies in slowly tempering desires into nothing, justice lies in tempering the balance of power so that all maintain equal shares, and virtue consists in tempering the body and soul into a balance of fitness, justice, and the good. Consequently the establishment of a clear definition of temperance ultimately serves as a foundation by which to resolve most of the dialogue's main issues.
This clarification and elevation of temperance frequently returns to Plato's writings throughout his life, since for him understanding and pursuing virtue (known now to be based upon temperance) represent the ultimate human activity.
Virtue
Defining virtue and its attainment comprise what is arguably THE central theme of both Gorgias and Plato's lifelong philosophical quest. Somewhat surprisingly, though, Socrates does not define this notion independently within the dialogue, but instead frames its nature by reference to other qualities he has worked to establish. In this light, virtue may be viewed as a composition of crucial topics: power, justice, temperance—all of which are associated with the good. Put differently, virtue is itself the 'good life', which results from proper practice of these various principles and behavioral methods. Considered from this perspective, then, the range of individual arenas of inquiry and subsequent discoveries about them here undertaken by Socrates melt into this more overarching, abstract notion.
This extrapolation towards virtue should not seem surprising, however, when placed in the context of Plato's life. To start, the war, corruption, and (wrongful) execution of Socrates for which Plato's government is responsible must have heavily influenced the thinker's search for virtue. The correlation between these historical aspects of Athens and the time of the dialogue's writing simply is too tight to deny. Moreover, each of Plato's dialogues almost without exception questions various aspects of proper living and what constitutes a good life. When taken together, Plato's entire body of creation looks to comprise an extremely comprehensive, long-term inquiry into the nature of virtuous living. Just as an understanding of abstract virtue gradually emerges from more specific sub-topics within Gorgias, so too does a general treatise on a complete life of virtue embody a unity among all Platonic dialogues.
