Nagel opens with an observation that is as uncomfortable today as it was in 1978. The great modern crimes are not committed by private criminals. They are committed by people with offices, titles, and institutional authority. And somehow, that authority insulates them.
He calls it a “slippery moral surface.” The office-holder acts not as a private person but as a functionary — servant of something larger than himself. A secretary of defense, a president, a general. The institution gets between the person and their acts.
This is not merely a structural observation. It is a psychological one. The role reshapes the person. The language of duty, of national interest, of responsibility — these are not neutral. They gradually colonize the private moral vocabulary.
But Nagel adds something sharper. The exercise of power, he writes, is “one of the most primitive human feelings — probably one with infantile roots.” Holders of public power are personally involved to an intense degree, and probably enjoying it immensely. The office is not merely a mask. It is also a reward.
The question, then, is the size of the gap. Between the person who signs the letters and the person who gives the speeches. Between the voice caught on tape and the voice broadcast to the nation. Some leaders maintain coherence. Others fracture. The Nagel Index measures which.
Abraham Lincoln left remarkably few public speeches and remarkably many private letters. The contrast between the Gettysburg Address and a personal telegram to a grieving mother is not merely a difference in occasion — it is a window into whether the institution changed him.
His private correspondence is direct, warm, self-deprecating, and occasionally melancholic. There is no performance of presidential gravity in a letter to his wife. The syntax is looser; the concerns are personal.
The Nagel Index finds a medium overall gap score of 0.41, driven primarily by Conscientiousness (d = 0.73) and Agreeableness (d = 0.53). But the raw score differences are tiny — never more than three percentage points on any trait. The effect sizes reflect how consistently the small shift appears across hundreds of text chunks, not how large the shift is.
This does not mean Lincoln was simple. It means he was consistent. The man who wrote “With malice toward none, with charity for all” in his Second Inaugural was the same man who signed condolence letters by hand. The institution did not transform him. This is the baseline.
Richard Nixon gave some of the most carefully constructed political speeches of the twentieth century. He also left behind 3,700 hours of secret White House recordings. The distance between those two archives is the story of a presidency.
On the tapes, Nixon is different. Not just in content — in texture. The vocabulary shifts from the lexicon of nationhood (america, spirit, peace, freedom) to the lexicon of operation (going, think, regard, course, concerned, matter). He sounds like a man running a machine, not leading a nation.
Nagel would not be surprised. The institution did not insulate Nixon from his moral failures — it amplified them. The office gave his paranoia jurisdiction. The question of whether Nixon was corrupted by power or brought his corruption to power is, perhaps, unanswerable. The gap only tells us that the two Nixons were measurably different men.
Kissinger is the hardest case. He appears in Nagel’s own essay — named as a man of high esteem despite the Christmas bombing of 1972 and “all that preceded it.” Nagel uses him as an example of exactly how the slippery moral surface works: the institution absorbs the act, and the man walks free.
His private vocabulary — secretary, policy, nsc, memorandum, files, staff — is the vocabulary of a system manager, not a statesman. In public he spoke of the world, of Mediterranean strategy, of the architecture of peace. In private he spoke of process.
Kissinger the thinker and Kissinger the operator were the same person. Kissinger the public figure was a performance.
This is what makes Kissinger interesting to Nagel’s framework. He was not transformed by the office. He used it. The institutional role was a tool he wielded deliberately — the “slippery moral surface” was, for Kissinger, a known instrument. That is a different kind of gap: not fracture, but strategic distance.
Aristotle’s Nicomachean Ethics gave the West its first catalogue of character-virtues — practical wisdom, justice, courage, temperance, and their kin. Alasdair MacIntyre’s After Virtue (1981) argued that the modern world had lost the shared vocabulary to reason about those virtues and was left emoting about moral fragments.
This project cannot say whether Lincoln was courageous or Nixon was just. But it can measure the vocabulary: how often each leader’s public speech and private writing reaches for six virtues drawn from Aristotle and MacIntyre.
The Nagel Gap does not measure morality. It measures distance — the linguistic and psychological distance between the self that spoke to history and the self that spoke when no one was supposed to be listening. A small gap does not make Lincoln a saint. A large gap does not make Nixon uniquely evil. Both were capable of cruelty. But only one of them was the same man in both rooms.
Nagel ends his essay with a provocation. The plausibility of the institutional excuse, he writes, is “inversely proportional to the power and independence of the actor.” The more power you hold, the less the office can absorb. At the very top, the gap between the person and the role collapses — what remains is just the person.
The data suggests he was right.
The Nagel Index compares personality scores extracted from two text corpora per leader — a public corpus of scripted institutional speech, and a private corpus of unscripted correspondence, press conferences, or internal memoranda. Everything below is drawn from open archives.
For each leader we assembled a public and a private corpus from public-domain archives. Years refer to the leader’s time in office; campaign-era material is included where available.
| Leader | Years | Public corpus | Private corpus |
|---|---|---|---|
| Abraham Lincoln | 1861–1865 | Miller Center presidential speeches | Library of Congress — Abraham Lincoln Papers, Series 1 |
| Thomas Jefferson | 1801–1809 | Miller Center | Founders Online — presidential series |
| George Washington | 1789–1797 | Miller Center | Founders Online — presidential series |
| Richard Nixon | 1969–1974 | American Presidency Project — inaugurals & State of the Union | American Presidency Project — news conferences |
| George H.W. Bush | 1989–1993 | American Presidency Project | American Presidency Project — news conferences & interviews |
| George W. Bush | 2001–2009 | American Presidency Project | American Presidency Project — news conferences & interviews |
| Henry Kissinger | 1969–1977 | FRUS press conferences & public statements | FRUS memoranda, meeting records & private correspondence (HistoryAtState mirror) |
Each document passes through a few mechanical steps: Unicode normalisation, removal of HTML and editorial footnotes, and a language check that drops anything not detected as English. Documents shorter than 150 words are skipped. The surviving text is cut into overlapping 400-word windows with 50% overlap — these are the chunks the personality model reads.
Every chunk is scored by Minej/bert-base-personality, a BERT model fine-tuned on the Big Five personality dimensions. Chunk-level scores are aggregated per leader into two distributions (public and private) and compared trait-by-trait with a Mann-Whitney U test and Cohen’s d effect size.
Cohen’s d expresses the distance between the two distributions in standard-deviation units — by convention, 0.2 counts as a small shift, 0.5 medium, and 0.8 or more large. The Nagel Gap Score shown on every dashboard is the mean of |d| across the five traits (we take the absolute value because we care how wide the gap is, not which voice scores higher on any given trait).
Keywords are extracted using log-likelihood — Dunning’s G² — rather than raw frequency. The measure identifies words that are over-represented in one corpus relative to another, which is a far stronger signal of distinctive vocabulary than "what appears most often." For every leader we compute two lists: the public voice versus the private, and the private versus the public.
The virtue-vocabulary scores come from a first-pass lexicon of six virtues drawn from Aristotle (Nicomachean Ethics) and MacIntyre (After Virtue): prudence, justice, courage, temperance, truthfulness, and magnanimity. Each virtue has 25–45 hand-picked marker words; per chunk we count exact-word matches and normalise by chunk length (hits per 1000 words). Correlations between virtue rates and Big Five scores are computed per leader and pooled across all seven, using Spearman’s rank correlation. The lexicon lives in the repo under data/virtues/lexicon.json and is explicitly treated as a starting point — it will be iterated on as the project’s understanding of MacIntyrean practice-virtues sharpens. Repeating the caveat from the Virtues act: this measures rhetorical emphasis, not moral character.
Each calligraphic split-face portrait is rendered by Google’s Gemini from a structured prompt that supplies the top 40 keywords per corpus. The four highest-ranking words per side are placed on forehead, cheekbone, jawline, and hair; the remaining words curve around the face as smaller text. The collar words — UNION / SEPARATION on Lincoln’s portrait — are synthesised by Gemini from the thematic arc of each word list.
A caveat before the numbers. Invoking virtue vocabulary is not the same as embodying the virtue — political speech tilts structurally toward abstract moral language whatever the speaker’s character. What follows is a measurement of rhetorical emphasis, not of souls. It is also a controversial move to place virtues and personality traits on the same page; the two come from different conceptual traditions, and aligning them is a provocation rather than a synthesis.
With that said, the pattern is worth naming. Lincoln keeps his virtue vocabulary roughly steady from public to private, and actually raises truthfulness and temperance in his correspondence. Nixon’s private voice drops nearly every virtue by a clear margin — truthfulness, magnanimity, courage all fall sharply, while prudence (strategic caution) is the only term that rises. Kissinger sits in the technocratic flat line he occupies on every other measure: few virtues in either register, a diplomat among process words.
When we correlate virtue-vocabulary rates with the Big Five at the chunk level across all seven leaders (n ≈ 3000 chunks, Spearman ρ), one result dominates: every virtue correlates positively with Conscientiousness, and nothing else consistently. Temperance tracks Conscientiousness most tightly (ρ ≈ 0.19, p < 0.001). The other four traits — Openness, Extraversion, Agreeableness, Neuroticism — tilt slightly negative across the board, which is what register, not character, would predict: formal moral language reads as structured rather than spontaneous, personal, or expressive.
What this adds to Nagel’s argument is modest. The office demonstrably shapes how a leader talks about virtue — the rhetorical register drifts with the institution. Whether it shapes whether they possess virtue is a question our vocabulary can indicate but not settle. The interesting case is the one where both the personality gap and the virtue-vocabulary gap move together: Nixon, whose private self loses not only measurable Extraversion but almost every moral term our lexicon looks for.