Homo unius libri (Latin, meaning "man of one book") is a phrase that is generally attributed to Thomas Aquinas.[1] According to a literary tradition at least three centuries old,[2] Saint Thomas Aquinas is reputed to have employed the phrase "hominem unius libri timeo" (meaning "I fear the man of a single book").


Aquinas's phrase has been interpreted in various ways. The literary critic Clarence Brown described the phrase in his introduction to a novel by Yuri Olesha:

"[Aquinas's] words are generally quoted today in disparagement of the man whose mental horizons are limited to a single book. Aquinas, however, meant that a man who has thoroughly mastered one good book can be dangerous as an opponent. The Greek poet Archilochus meant something like this when he said that the fox knows many things but the hedgehog knows one big thing."[3]

Joseph Needham, in the general conclusions to his masterwork, the series Science and Civilisation in China, observed of the familiar tag, "It could mean that this man has only read one book, has only written one book, does not possess more than one book, or puts his faith in one book only. The fear that is felt may be on behalf of the man himself. Having read so little he is quite at the mercy of his one book!"[4]

The poet Robert Southey recalled the tradition in which the quotation became embedded:

"When St Thomas Aquinas was asked in what manner a man might best become learned, he answered, 'By reading one book'; 'meaning,' says Bishop Taylor, 'that an understanding entertained with several objects is intent upon neither, and profits not.' The homo unius libri is indeed proverbially formidable to all conversational figurantes. Like your sharp-shooter, he knows his piece perfectly, and is sure of his shot." — Robert Southey, The Doctor, p. 164.

Southey quotes Lope de Vega in the same vein:

Que es estudiante notable
El que lo es de un libro solo.
Que quando no estavan llenos
De tantos libros agenos,
Como van dexando atras,
Sabian los hombres mas
Porque estudiavan en menos.[5]

Southey's version of the quote was taken up by John Bartlett (1820–1905), the compiler of Bartlett's Familiar Quotations (ninth edition, 1902, p. 853).

The familiar thought was paralleled by the Augustan poet Alexander Pope:

A little learning is a dang'rous thing;
Drink deep, or taste not the Pierian spring:
There shallow draughts intoxicate the brain,
And drinking largely sobers us again. — Essay on Criticism, Part ii.15.

Edward Everett applied the remark "not only to the man of one book, but also to the man of one idea, in whom the sense of proportion is lacking, and who sees only that for which he looks."[6]

Aquinas' phrase was consciously turned on its head by John Wesley, who informed a correspondent that it was "in 1730 I began to be homo unius libri, to study (comparatively) no book but the Bible."[7] He wrote privately on another occasion

"I receive the written word as the whole and sole rule of my faith..... From the very beginning, from the time that four young men united together, each of them was homo unius libri... They had one, and only one, rule of judgement with which to regard all their tempers, words and actions; namely, the oracles of God."

Wesley used it more publicly in the Preface to his collected sermons;

"He came from heaven; He hath written it down in a book. O give me that Book! At any price, give me the Book of God. I have it; here is knowledge enough for me. Let me be homo unius libri!"

Wesley's point, made emphatic through hyperbole, was the primacy for him of Scripture. Tradition, reason and experience, along with scripture were all part of his hermeneutical model. They were, however, not all equal: the Bible was sufficient. Wesley's spiritual heirs, in the Book of Discipline of the United Methodist Church (1996) affirm that:

"Wesley believed that the living core of the Christian faith was revealed in scripture, illumined by tradition, vivified in personal experience and confirmed by reason."

Like Methodists in the strict Wesleyan tradition of depending upon the One Book, many seventeenth century and modern radical Protestants pride themselves on being homines unius libri. The poet William Collins in his deranged condition, met by chance his old friend Dr. Samuel Johnson, who found Collins carrying a New Testament. "I have but one book," said Collins, "but it is the best". Collins' epitaph in Chichester Cathedral reads, in part:

Sought on one book his troubled mind to rest,
And wisely deemed the book of God the best.[8]

The writer and naturalist Charles Kingsley, following the tradition laid down by Gilbert White in The Natural History and Antiquities of Selborne (1789), invoked the proverb in favour of knowing completely one small area. "A lesson is never learnt till it is learnt over many times, and a spot is best understood by staying in it and mastering it. In natural history the old scholar's saw Cave hominem unius libri[9] may be paraphrased by, 'He is a thoroughly good naturalist who knows one parish thoroughly.'"[10]


  1. On the other hand, The Concise Dictionary of Foreign Quotations, Anthony Lejeune, editor, (London 1998) attributes the quote instead to Augustine of Hippo.
  2. Bishop Jeremy Taylor (1613 - 1667) is the earliest writer in English to have noted the assertion.
  3. In The Portable Twentieth-Century Russian Reader, Clarence Brown, editor (Penguin) 1985, p. 246; see The Hedgehog and the Fox for further discussion of this phrase.
  4. Science and Civilisation in China, "50 General Conclusions and Reflections", p. 97.
  5. From "Isidro de Madrid", by Lope de Vega, published in Obras Sueltas. Translation:
    For a noteworthy student is he,
    The man of a single book.
    For when they were not filled up
    With so many extraneous books,
    As they progressed in study,
    Men used to know the more
    Because they studied from fewer.
  6. Reported in William Shepard Walsh, Handy-book of Literary Curiosities, 1892, s.v., "Book, Beware of the man of one".
  7. Letter to John Newton, May 14, 1765.
  8. The Johnson anecdote and Collins' epitaph are reported in Walsh 1892 s.v., "Book, Beware of the man of one".
  9. "Beware the man of one book."
  10. Charles Kingsley, At Last: A Christmas in the West Indies, 1871.

External linksEdit

it:Timeo hominem unius libri tr:Timeo hominem unius libri

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