Good and Evil
A Wrinkle in Time is a classic novel about the battle between good and evil. Meg, Charles Wallace, Dr. Murry, and their friends all fight on the side of good, which is defined by its ability to make friends, feel love, and discern the difference between right and wrong. Meanwhile, IT, the Man with the Red Eyes, and the Dark Thing (the figure of Death) are all agents of evil. IT is the villain and antagonist of the novel, using its psychic powers as a gigantic brain to mind control the people of Camazotz. In so doing, IT strips the people of their free will, forcing them to obey its commands instead of acting on their own behalf. IT also imprisons Dr. Murry, a gifted scientist whose job it was to fix the social problems IT caused on Camazotz. IT's tyrannical behavior stems from its lack of a conscience. This ultimately makes IT vulnerable to the forces of good, which employ different weapons (love instead of mind control, for instance) to defeat their enemies. In the end, Meg is victorious.
Free Will and Conformity
One of the intended side-effects of mind control is conformity. When IT uses its mental powers on the citizens of Camazotz, it effectively strips them of their free will, making it impossible for them to make their own choices or even to resist. Consequently, the people act according to IT's will and are forced to conform to the ideals that IT has ascribed. IT believes that total submission to its will is the greatest form of bliss, but L'Engle makes it clear that this isn't the case. Under IT's control, a person is largely incapable of feeling love, sadness, and the full range of human emotions. This is a dangerous form of conformity that seeks to strip people of what makes them human.
L'Engle makes it clear in the title of the novel that she's going to be playing with the theme of time. Time isn't chronological in this narrative, not because the narrator moves back and forth in time but because the characters quite literally travel through a bend in space and time called a "tesseract." In moving through time this way, L'Engle shows us her vision of the future, where science is far more advanced and people are capable of bending time to their will. This places A Wrinkle in Time firmly in the realm of science fiction.
In A Wrinkle in Time, knowing that you don't know something is as important as actually knowing it in the first place. Meg's hunger for clear, concrete explanations to everything, even to people, makes her a difficult character at the beginning of the novel. Her mother must tell her to be patient and get to know Calvin O'Keefe before making any judgments. Ultimately, Meg and Charles Wallace accept the fact that they can't know everything. This realization helps them on their quest.
Love conquers all is a central theme in A Wrinkle in Time. L'Engle depicts love as a powerful force capable of triumphing over evil. Love is what binds Meg, Charles Wallace, and their father together, and it's what allows Meg to defeat the evil IT, who could not be destroyed through reason, violence, or even Charles Wallace's special abilities.