From Flannery O'Connor's short story, "Good Country People":
She was brilliant but she didn't have a grain of sense. It seemed to Mrs. Hopewell that every year she grew less like other people and more like herself--bloated, rude, and squint-eyed. And she said such strange things! To her own mother she had said--without warming, without excuse, standing up in the middle of a meal with her face purple and her mouth half full--"Woman! do you ever look inside? Do you ever look inside and see what you are not? God!" she had cried sinking down again and staring at her plate, "Malebranche was right: we are not our own light. We are not our own light!" Mrs. Hopewell had no idea to this day what brought that on. She had only made the remark, hoping Joy would take it in, that a smile never hurt anyone.
The girl had taken in a Ph.D. in philosophy and this left Mrs. Hopewell at a complete loss. You could say, "My daughter is a nurse," or "My daughter is a schoolteacher," or even, "My daughter is a chemical engineer." You could not say, "My daughter is a philosopher." That was something that had ended with the Greeks and Romans. All day Joy sat on her neck in a deep chair, reading. Sometimes she went for walks but she didn't like dogs or cats or birds or flowers or nature or nice young men. She looked at nice young men as if she could smell their stupidity.
Malebranche does indeed insist that we are not our own light; it's actually a quotation from Augustine, whom Malebranche quotes often, and it is far and away his favorite quotation. It comes up repeatedly in the long dispute with Arnauld, because from Malebranche's perspective (although, of course, not from Arnauld's), Arnauld is denying Augustine's dictum by denying Malebranche's claim that we see all things in God.
I don't know how much O'Connor knew about Malebranche, but this scene is beautifully done. There is considerable irony in Joy's (or, to use the name she prefers, Hulga's) reference to Malebranche here. Malebranche, of course, has a thoroughly theistic metaphysics and epistemology; when he is quoting this line from Augustine (who is making a point about our metaphysical dependence on God in our ability to know), he is making a thoroughly theistic point. But Hulga, of course, is an atheist and nihilist. Nonetheless, her description here, if taken in a literal way she didn't intend, describes Malebranche's point to a T. "Do you ever look inside and see what you are not? God!" The last bit is clearly just a cry of exasperation; but the whole thing describes a good portion of Malebranche's argument, which is that when we look in side we see that we are not God, we are not a light to ourselves; it is in His light that we see light. But of course, she is making the opposite point, that we are nothing, that there is nothing to believe in, the sort of thing O'Connor has her reading in the book that strikes simple Mrs. Hopewell as an "evil incantation":
One day Mrs. Hopewell had picked up one of the books the girl had just put down, and opening it at random, she read, "Science, on the other hand, has to assert ist soberness and seriousness afresh and declare that it is concerned solely with what-is. Nothing--how can it be for science anything but a horror and a phantasm? If science is right,t hen one thing stands firm: science wishes to know nothing of nothing. Such is after all the strictly scientific approach to Nothing. We know it by wishing to know nothing of Nothing."
As she describes herself later on, "I'm one of those people who see through to nothing."
Malebranche has an interesting passage in which he talks about seeing nothing (Search 3.2.8, Lennon-Olscamp 241):
The clear, intimate, and necessary presence of God (i.e., the being without individual restriction, the infinite being, being in general) to the mind of man acts upon it with greater force than the presence of all finite objects. The mind cannot entirely rid itself of this general idea of being, because it cannot subsist outside God....One might well not think about oneself for some time, but it seems to me one cannot subsist a moment without thinking of being, and at the very time that one takes himself to be thinking of nothing, one is necessarily filled with the vague and general idea of being.
As Malebranche says later, "nothingness is neither perceptible nor intelligible" (LO 321); what we call 'nothing' is really just nothing in particular. But nothing in particular is not being-less; it is being in general, without consideration of how it relates to any particulars. And on Malebranche's metaphysics, being in general, as an object of thought, is divine (unrestricted being). So for him, someone who is "seeing through to nothing" is really just seeing being in general in the divine being, without recognizing it as such. In her allusion to Malebranche, Hulga has (without apparently realizing it at all) entangled herself in a rather massive philosophical irony, one that (I hate to use the word, but it'll do) subverts her own nihilism by juxtaposing it with its complementary opposite.
I find that students of O'Connor tend not to think that she was deliberately engaging in irony there. Of course, students of O'Connor tend not to realize that there is any irony in the situation. A typical instance seems to be Ralph C. Wood:
This is an apt, if pretentious, allusion for Hulga the Heideggerian to make, for Malebranche stands in the Cartesian tradition that runs from Hume and Berkeley through Kant and Heidegger. Malebranche held that we do not, in fact, see by our own light but by what he called "vision in God." He was obsessed with the Cartesian problem of human knowledge about objects outside themselves. Together with Descartes, he argued that knowledge of the world does not come from either sensation or imagination but from clear and distinct ideas perceived by the understanding. Yet unlike his master -- and much closer to Spinoza -- Malebranche held that "created things are in themselves causally inefficacious and that God is the sole true cause of change in the universe" (Willis Doney, "Malebranche, Nicholas," in Encyclopedia of Philosophy, Vol. V, ed. Paul Edwards [New York: Macmillan, 1967], p. 140). Malebranche's denial of the mind's ability to perceive truth through the natural order of things, together with his denial of secondary causes and thus of real human freedom, would make Hulga an ideal disciple of so unsacramental a thinker.
[Ralph C. Wood, Flannery O'Connor and the Christ-Haunted South (Grand Rapids, Michigan: Eerdmans, 2005), p. 201n.]
There are a number of confusions here (I wasn't aware that the Cartesian tradition ran from Berkeley to Heidegger, which is a new twist on the history of philosophy). But whereas I would suggest that Hulga's taste for Malebranche is highly ironic -- Malebranche is explicitly and aggressively Catholic, and his ontologism is in severe contrast to Hulga's nihilism -- Woods treats them as well-matched. I think there are two questions raised by this:
(1) What is the real function of Malebranche in "Good Country People" and are there any Malebranchean links in other stories?
(2) What did O'Connor actually know about Malebranche?
With regard to (2) I find Wood's interpretation rather implausible; surely O'Connor would have heard enough of Malebranche to know that he was both a Catholic and an ontologist -- she knows at least enough that she has Hulga quote Malebranche's favorite quotation from Augustine, although it's not impossible that she didn't recognize that it was a quotation. So that's perhaps a third question:
(3) Did O'Connor recognize the original Augustinian implications of the statement, "We are not our own light" or did she interpret it in another way?
There is, related to this, another irony that I did not mention in the first post: namely, that Hulga's entire problem throughout the story is that she acts as if she were her own light. This confidence in her own intellect is what allows her to be deceived by Pointer.
O'Connor's use of, and knowledge of, Malebranche is certainly a worthwhile research project, if there's anyone out there interested in doing it.