The conversation moves on to explore the nature of power, with eager young Polus taking the reigns from his master Gorgias. Polus initially declares power to be something good for its possessor, a claim that exists as equivalent to the one that power is the ability of its possessor to achieve the end of the good through their actions.
This statement in turn prompts Socrates to argue that if this definition is correct, then tyrants have the least power of any in a given state. Such a declaration appears initially to run counter to instinct, but Socrates's simple subsequent explanation of the case as he sees it helps quickly to clarify the situation. Essentially, humans tend to will not an action itself but rather they will "that for the sake of which they act as they do." This principle may be extended to serve as a governing principle of all human action. As regards medicine, for example, one does not take a particular remedy for its own sake, but instead does so in order to improve his/her health. The outcome of this action, rather than the action itself, represents the true aim. Put differently, "[i]f a man acts with some purpose, he does not will the act, but the purpose of the act." This holds most notably across the arts. With each instance of a patterned skill, the practicing of the trade in question is not good for its own sake, but rather for the sake of some benefit that arises from the performance of the particular action. In this way, a man does not practice the art of fitness training because running unending distances is good for its own sake, but instead because the state of physical health which emerges from such a strict regimen is good for the body and soul and therefore the human's existence. The same holds for any other art, for this is just what it is to be a true art: an action which is good not on its own but in terms of the good which results from its performance, whether under the category justice, temperance, medicine, gymnastics, or any other one.
From here Socrates jumps to the parallel consideration of a powerful tyrant. As he frames the issue, a strong leader often faces situations (for example) in which someone must be punished or even executed for the good of the state. In such an instance, the ruler does what he believes to be good, thereby bracketing the action within the realm of Polus's definition of power as good for its possessor. Socrates furthermore claims that in this type of situation (just as with the example of medicine), the ruler does not will the action of punishment or execution, but instead wills its outcome of benefit to the state. Authoritative tyrants are therefore shown nonetheless not to possess true power, since they still must perform actions they do not voluntarily will.
It should here be noted that Polus's definition of power, rather than that of Socrates, is the one that makes reference to the good. It would seem (given Socrates more overarching interest in defining what is good living) that the philosopher of ethics rather than the student of rhetoric would put forth such an inclusive-of-the-good conception of power. Yet this is not the case.
Socrates's main proof here derives its force from a fairly formal use of logic. One would be hard pressed to deny the proposition that humans will not actions themselves, but their outcome instead. This claim simply seems to signify a fundamental aspect of human existence. For example, one does not eat for the sake of eating so much as for the eradication of hunger, even if it might be enjoyable. To be sure, many actions are enjoyable in and of themselves. It would seem that things like eating, and sleeping, making love, watching sunsets, or any other of a large number of pleasurable activities possible for humans to perform fall under this category. Anything enjoyable might be definable as an action enjoyable for itself. Plato's point maintains a different thrust, however. Instead, he means to emphasize that any such action is not performed for the reason of itself and its own performance, but rather for the very sake of the enjoyment which comes with its performance. Were the act not somehow pleasurable, it would not be performed (without some other reason for the action). Even actions whose sole utility is pleasure are executed not for themselves, but for the pleasure that accompanies them.
Furthermore, Plato restricts his discussion to include not all pleasurable activities, but only those that target the good, since he is ultimately concerned only with what is the good. This limitation of the focus foreshadows not only the looming distinction of pleasure from the good (with all its ramifications) as well as Plato's coming definition of temperance, but also his unifying focus in Gorgias of virtue.