Free will versus conditioning
Every major plot turn tests whether Alex can choose his own behavior. The Ludovico Technique removes that choice mechanically. Burgess treats this as a moral catastrophe worse than Alex's crimes, because the state acts without conscience and calls it progress.
State power and the individual
The government in the novel uses Alex as a demonstration project. It doesn't care about him as a person. The opposition does the same. Both sides treat Alex as a means to a political end, and the novel shows how institutions crush individuality even when they claim to help it.
Youth, violence, and growing up
Alex's violence is partly adolescent energy with nowhere to go. The twenty-one-chapter structure mirrors the age of maturity. By the final chapter, Alex starts to outgrow his own brutality, not because anyone forces him to, but because he gets older and bored with it.
Language as control and identity
Nadsat is Alex's language, and it keeps him separate from the adult world. It also controls the reader's experience of violence. Whoever controls language shapes reality, and Alex's slang is his one form of power that nobody can condition away.
Morality without choice is meaningless
Burgess argues that goodness only counts if it's chosen. A person who cannot do evil is not virtuous, just broken. This theme runs from the Ludovico sessions all the way to Alex's voluntary decision to change in the final chapter.