In what instances are ideals seen in the plot of Les Miserables? none
If by ideals, you mean standards of moral behavior, there certainly are plenty of instances in this novel to explore this motif. Hugo was determined to glorify the beauty, resilence, and ulitmate goodness of humanity in the face of a cruel and unforgiving society. Therefore, moments of "revelation" are rife!
The earliest and, some may argue, most significant moment occurs between Valjean and the Bishop. The Bishop, having been abused by the convict, is not only forgiving of Valjean, but also generous and loving towards him. He insists, despite the objections of his own housemates, that Valjean is likewise a child of God, and therefore a man worthy of love. Valjean begins to question his cynical judgments of the world.
The next instance that illuminates Hugo's ideals comes shortly after, when Valjean meets Petit Gervais. Valjean has not yet left behind his cold, calculating persona. He deliberately steps upon the child's coin. However, lost in a reverie of recollection, Valjean allows the Bishop's words and actions to effect change upon him, and spends his life attempting to find and repay the small theft he committed.
Valjean's amnesty, as Mayor, towards Fantine is another instance in which the ideals are portrayed. He is not only atoning for his own mistake in allowing her to be fired, but recognizing the parallels between his and Fantine's stories. They were both, to extent, products of the environment they lived in. Choosing to care for her, and then for her daughter, demonstrates Valjean's acceptance of the moral ideal over the idea of social success.
Skipping over many instances for the sake of brevity, lets focus on Javert's personal revelation. When Valjean spares his life, Javert faces a truth he never allowed. He understands that a man can be morally good and socially bad. A man can break society's laws and still uphold God's law. Javert, believing himself to be pious, had never thought that could be true. His suicide, while tragic, glorifies the ideal of moral supremacy over social justice - he can't live with the things society has made him do, understanding at last that he has blasphemed God in the name of his occupation.
If you are talking about ideals, you could meaning the ethical behaviors of the characters in the story, revealing which one is real or sincere, and which what is fake and misleading. There are plenty of these stuffs in the novel to explore this theme. In this story, the author, Victor Hugo explore was trying to signify the "Miserables" meaning the poor scoundrels and villains of the story, painting a detailed expression of Paris's seamier side and also to discuss the cause and effect of the long-ravaging revolution in the making. He is trying to glorify that there is still glory and honor and beauty and happiness in mankind's world in these troubling and horrible times of the "menace" society.
Through Valjean, the theme of "ideals" is most clearly expressed. He is the main protagonist of the entire story, who is once an ex-convict who wanted to find redemption and reconciliation and struggles to redeem himself morally and to find comfort in the society, who had already branded him as a "hate figure". The ideals was most clearly conveyed through the chanced meeting with the Bishop of Digne, who even after Valjean had tried to steal something from his household, who forgave him for his past misdeeds, accepted him for who he was and shelters him regardless for his past, showing unconditional love traveling no boundaries and frontiers, showing generosity and benignity to people in desperation. Bishop even treated him as a honorable guest and he called Valjean monsieur. Even when he had taken his silver, he still asked him to keep the silver and also counseled him to be a better person.
The next scenario was when he had encountered a young musician from Savoy who entertains with a hurdy-gurdy and a marmot. He had still not revert from his normal behavior and behave in a tyrannical and barbaric manner, when he took a 40-sous piece from him, even though he had been pleading and crying for him to stop. Overwhelmed by guilts and thoughts of meeting the Bishop, he was overwhelmed with remorse and tried desperately to find the boy and return back the coin.