"Even things that are true can be proved..."See in text(The Preface)
This is an example of a typical Wildean paradox. Obviously, things that are true can be proved. However, Wilde adds irony to this statement to provoke curiosity among his followers, and discomfort among his critics.
Literally paraphrased, it means that you cannot "read into art" the way you would read into a history or a science book, for example, where there are clear patterns and trends established by facts.
"Philanthropic people lose all sense of humanity..."See in text(Chapter III)
This is another great example of Wilde's use of paradoxes to contradict accepted concepts. The true philanthropist would generally be thought to gain all sense of humanity, not lose it.
"Pure family affection, I assure you, Uncle George. I want to get something out of you..."See in text(Chapter III)
This is one of the novel's many paradoxes. Following "pure family affection" with "I want something from you" exemplifies Wilde's signature contradictory statements.
