In the Ransom series, the number of self-deceived people in the first two books is small, because the number of characters is small. In Out of the Silent Planet, Devine has been deceived by Weston, but seems to have participated in this and embraced it. It is Weston who is entirely self-deceived, fixated on his own importance at first, but tinged with the idea that he is accomplishing some great work that will benefit all mankind. While this great cause seems a mere excuse at first for his personal ambitions, it is clear by the end that he does believe a great deal of it. Lewis uses a clever device of having Ransom translate Weston's pompous speech to the Malacandrians into Old Solar, in order to lay bare the vacuity of the underlying ideas of colonising unfallen planets. It is a foreshadowing of Perelandra, in which Weston is now very much convinced of the idea of bringing the evil of earth to unfallen Venus. We see rapidly that Weston is not entirely his own master by this point, infected or even inhabited by something darker. Yet we know that this conquest of his soul has been with his entire cooperation, and even near the end, after Ransom has suddenly turned in surprise and asked "Are you Weston?" he believes he could still come free by an act of will if he would only make some effort. "Pull yourself together. All that stuff you've been talking is lunacy. Say a child's prayer if you can't say a man's."
The third book of the series That Hideous Strength is awash with people deceiving themselves, most of them academics and fringe science-y people. Small wonder that Lewis, very used to watching academics deceive themselves could capture them so convincingly. The main two stories (of seven, as I recently noted) revolve around Mark and Jane Studdock, nice enough young people who have been on the road to deceiving themselves these last few years but are not yet far gone. (I will have to write soon about how the intrusion of the Merlin/Logres plot, which Tolkien felt was due to the influence of Charles Williams and the destruction of an otherwise decent book, creates the most unfair criticism leveled against Jane. A topic for another day.) Jane brings some self-deception from her own beliefs of what a modern woman in general should be like, which prevent her from seeing some obvious things about herself individually. Yet it is Mark who is deeper in, more vulnerable, and more in need of rescue. The various players at the N.I.C.E. are attempting to deceive and manipulate him, yet they are playing off his ambition and need for flattery to achieve it. He gets warnings along the way, including from the only first-rank scientist in the bunch, Bill Hingest, who resigns and tells Studdock to get clear as soon as possible. Mark is being invited, not for his academic value as he supposes, but because of his own facility with words, to be used to manipulate local opinion. (Also, so that they may get at his wife's mystical abilities, part of another plot.) It is in this context that Mark has it explained to him by the head of the rapidly-growing secret police of the N.I.C.E. that the target of this is not the common people he believes so susceptible to manipulation in the press, but his own people, the educated. It is likely the most often quoted section in the book.