This Is Water (2005 Kenyon College Commencement Address)

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TL;DR

Wallace's only public statement of his worldview in plain didactic prose (delivered 21 May 2005; published as a book 2009). Archived copy is the 6-page transcription of the speech as delivered. It restates IJ's deep arguments — everybody worships, the self is a default-setting prison, freedom is trained attention — a decade later and without fictional armor: the single-entendre-values program of E Unibus Pluram carried out literally.

Key claims

The fish parable: "the most obvious, important realities are often the ones that are hardest to see and talk about" — stated as "a banal platitude" that is nonetheless life-or-death "in the day to day trenches of adult existence." Same move as IJ's AA clichés: banality as vehicle for vital truth (cf. the Salon interview on "One Day at a Time").
The "default setting": we are each "uniquely, completely, imperiously" the center of our own experience — hard-wired self-centeredness as the ground-state. This is IJ's cage/solipsism theme ("marooned in her own skull," from McCaffery) generalized to everyone.
"Everybody worships. The only choice we get is what to worship." Worship money, body, power, intellect — "pretty much anything else you worship will eat you alive." This is Marathe's argument to Steeply almost verbatim (choose your attachments with care; temple vs. Entertainment), and the addiction theme abstracted: an addiction is an unchosen worship.
The insidiousness claim: such worship is dangerous not because it's evil but because it's "unconscious... default settings" — you slide into it "day after day" without ever realizing you're choosing. Compare the Erdedy and Hal pot sections and the essay's TV-addiction spiral.
Real freedom = "being conscious and aware enough to choose what you pay attention to and to choose how you construct meaning from experience" — "being able truly to care about other people... over and over in myriad petty, unsexy ways every day." Anticipates The Pale King's boredom/attention thesis (cf. The Unfinished, which quotes this speech as the bridge).
The stakes are IJ's stakes: the unwitnessed routine of adult life, the "rat race" as "the constant gnawing sense of having had, and lost, some infinite thing" — and, darkly, his aside that "it is not the least bit coincidental that adults who commit suicide with firearms almost always shoot themselves in: the head."

Themes

Addiction (worship as its general form); communication/solipsism (the default setting as the cage; empathy as discipline rather than feeling); entertainment (the comfort of the default vs. effortful attention); AA-style banal wisdom elevated to commencement-speech form.

Cross-references

McCaffery interview: the loneliness/ self-entrapment diagnosis this speech popularizes.
E Unibus Pluram: this is the anti-rebel performance — endorsing single-entendre values while flagging their banality ("I am not the wise old fish").
The Unfinished: quotes the speech; positions it between IJ and The Pale King.
IJ connections: Marathe/Steeply dialogues on worship and choice; AA's "Abide" and cliché pedagogy; Hal's anhedonia and the "infinite thing" lost; the Entertainment as terminal default-setting indulgence.

Notable passages

"There are these two young fish swimming along and they happen to meet an older fish swimming the other way, who nods at them and says 'Morning, boys. How's the water?'... 'What the hell is water?'"
"The most obvious, important realities are often the ones that are hardest to see and talk about."
"Everybody worships. The only choice we get is what to worship."
"[True freedom] means being conscious and aware enough to choose what you pay attention to and to choose how you construct meaning from experience. Because if you cannot exercise this kind of choice in adult life, you will be totally hosed."