In Section 3 - Thrasymachus and the Rejection of Conventional Morality - of Part I of The Republic, Socrates is faced with a fierce (albeit petty) advocate of "justice as the interest of the stronger" in the form of Thrasymachus.
It is noteworthy that Socrates, a proponent of virtue and objective morality, never really deals convincingly with this postulation that the more powerful person determines what justice is. Such thinking is embedded in the realist school of thought, with its subsequent and significant catchphrases like 'history is written by the winners', 'those in power determine everything' and 'might is right'. When one thinks of justice as essentially a system of fairness and the restoration of equity, one realizes that 'justice' is really a plaything in the hands of realists.
That is not to say that Socrates' idealism is worthless. Socrates appeals to the idea that there is a fundamental good, and although it is difficult for mere human mortals to pinpoint what it is, we can all agree that it all stems from life itself. Throw a baby in a swimming pool and it struggles to survive. Another is possibly social relationships. We cannot do without our parents, and we often cannot do without friends. There are certain tendencies that are part of our nature qua human beings. That is why I think it is morally correct to respect life, which relevantly makes any issues dealing with life, especially the termination of it, difficult ones. The fact that most of us can agree that humanity flourishes when there are things like love, justice, harmony and goodness instead of hate, injustice, disunity and evil is indicative of some objective good, morality or truth.
On the other hand, Thrasymachus is a realist who believes that injustice pays more - obviously the just man is going to come off worse in a transaction with an unjust man who is going to undercut him. Thrasymachus postulates from a position that is fundamentally competitive and subjective - justice is served by whoever has the power to wield it.
Essentially, Socrates posits an argument of justice based on objective morals, while Thrasymachus posits an argument of justice based on competition for profit.
In reality it is extremely impractical to follow through on Socrates' recommendation. Anybody who wants to right the wrongs of a few thousand years by setting an example of himself based on Socrates' virtues as a just man is bound to perish, because the system we live in provides no sympathy or room for a heart of gold. However, Socrates appeals very deeply to me because of the very romantic idea that there is the possibility of ideal goodness. In this daydream, one sees how rotten to the core we are, as we exist so far away from that ideal today.
What's the prescription for utopia, one might ask. Ideally, we should rely less on the government, because the legal system simply cannot cover every dispute. In other words, there can't be rules on the right thing to do for everything. Teach kids well about what makes a good man of virtue and excellence, and let that be the guiding light that fills in the gaps of the legal system, and that lead him or her to go through life with other people well.
Singapore is easily the country with the most rules and laws on this planet. Singaporeans have internalized the rules accordingly, and parents teach their kids from young to be competitive and that it is good to be better than others and make more money than everyone else. What results is a rigidity and inflexibility captured well in kiasu-ism that is unparalleled anywhere else. But what else can we expect from being run by possibly the best practitioner of realism and the most exemplary student of Macchiavellianism?