Symbolism, Imagery, Allegory
Got Ultraviolence?
What would you expect a gang of rapists and murderers to drink? Maybe whiskey—it's what grizzled black-hat cowboys tend to drink. Or maybe water—something about the purity and cleanliness of water would juxtapose nicely with violent crime. Or even, say coffee—we're familiar with the coffee-before-carnage trope from films like Reservoir Dogs.
Nope. Alex and his droogs drink...milk.
Okay, sure: they drink "milk plus," or milk laced with vellocet, synthemesc, and drencrom. (These fictional drugs, which seem to be partially hallucinogenic and partially amphetamine-like, amp up the boys for a night of the old ultra-violence.) But the fact remains: they're slurping down moo juice.
Not only that, but Alex drinks milk with almost every meal. Is he calcium deficient? Does he need more Vitamin D? Probably not—most likely, Burgess is making a point about innocence.
Milk is the drink of choice (er—without the "choice" part) for infants. It's what a lot of well-meaning parents give their kids to drink at dinnertime. It's synonymous with childhood, and therefore synonymous with sweet, youthful innocence. But of course Alex & Co. are anything but innocent—they're fiends.
You can read the symbolism of milk in one of two (main) ways: either Alex and his droogs are corrupted youth, as poisoned as a glass of drug-laded milk. Or they are, in fact, kids—their approach to violence is one of joy: they seem to approach each rampage with a kind of childish enthusiasm.
Which reading you prefer depends on how pitch-black you want Burgess' novel to be. Either Alex is a bad apple, an exception to the rule of fifteen-year-old innocence...or there's a strain of violence in even the most cherubic kiddo. Either Alex is like drugs in milk—a shocking juxtaposition of adult mayhem in a young teen's body—or he represents a violence that's as ubiquitous in all humanity as milk in a baby's meal schedule.