Learn English – What word means “the top of a person’s head”

Apophasis is the term.

OED defines the term by quoting John Smith's The Mysterie of Rhetorique Unvail'd (1657):

a kind of Irony, whereby we deny that we say or doe that which we especially say or doe.

Here is the definition from grammar.about.com:

A rhetorical term for the mention of something in disclaiming intention of mentioning it--or pretending to deny what is really affirmed. Adjective: apophatic or apophantic. Similar to paralepsis and praeteritio.

_{Wikipedia mentions that it is a rhetorical relative of irony and lists the following equivalents:}

_{Also called paralipsis (παράλειψις) – also spelled paraleipsis or paralepsis –, or occupatio, and known also as praeteritio, preterition, cataphasis (κατάφασις), antiphrasis (ἀντίφρασις), or parasiopesis (παρασιώπησις).}

I do not have the Norton Critical Edition of Burgess’s novel to hand, but I would strongly suspect that the word is anagnorisis (ἀναγνώρισις), a term of art in Aristotle’s analysis of tragedy, meaning recognition or discovery:

A “discovery,” as the term itself implies, is a change from ignorance to knowledge, producing either friendship or hatred in those who are destined for good fortune or ill. A discovery is most effective when it coincides with reversals, such as that involved by the discovery in the Oedipus. There are also other forms of discovery, for what we have described may in a sense occur in relation to inanimate and trivial objects, or one may discover whether some one has done something or not. But the discovery which is most essentially part of the plot and part of the action is of the kind described above, for such a discovery and reversal of fortune will involve either pity or fear, . . . [Poetics 1452a]

Aristotle is being very general here as usual, but Alex’s recognition surely qualifies.