He is developing his idea gradually in a series of positions or situations.

He is exhibiting Socrates for the first time undergoing the Socratic interrogation.

Lastly, (3) the word 'happiness' involves some degree of confusion because associated in the language of modern philosophy with conscious pleasure or satisfaction, which was not equally present to his mind.
Glaucon has been drawing a picture of the misery of the just and the happiness of the unjust, to which the misery of the tyrant in Book IX is the answer and parallel.

And still the unjust must appear just; that is 'the homage which vice pays to virtue.' But now Adeimantus, taking up the hint which had been already given by Glaucon, proceeds to show that in the opinion of mankind justice is regarded only for the sake of rewards and reputation, and points out the advantage which is given to such arguments as those of Thrasymachus and Glaucon by the conventional morality of mankind.

He seems to feel the difficulty of 'justifying the ways of God to man.' Both the brothers touch upon the question, whether the morality of actions is determined by their consequences; and both of them go beyond the position of Socrates, that justice belongs to the class of goods not desirable for themselves only, but desirable for themselves and for their results, to which he recalls them.