In Chapter 39, when Pip's true patronage is revealed, Dickens describes the unreadable feelings displayed on Provis's face through the use of a paradox. As the returned convict gazes at Pip, the narrator describes his expression as
A smile that was like a frown, and with a frown that was like a smile.
This description is almost an oxymoron, as the two similes would usually cancel each other out. A frown is usually considered to be the opposite of a smile. The fact that Pip cannot tell which expression the older man is making illustrates how discomfited he is by the interaction. The paradoxical nature of this expression also reflects Provis's dominance over the situation, as Pip cannot interpret his purpose. Provis has been waiting a long time to explain to Pip how he has been supporting him, and by making his face this unreadable, he prolongs the agony of suspense for Dickens's protagonist.
This exchange between Pip and an older man also echoes another more conventional oxymoron that refers to a facial expression—the one made by the pompous Mr. Pumblechook in Chapter 29. When Pumblechook gives Pip a "frowning smile," he is also showing his dominance of a situation by asking a series of leading questions to draw Pip to a desired conclusion.