Homo unius libri

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Homo unius libri ('(a) man of one book') is a Latin phrase attributed to Thomas Aquinas by bishop Jeremy Taylor (1613–1667), who claimed that Aquinas is reputed to have employed the phrase "hominem unius libri timeo" ('I fear the man of a single book').

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."[1] 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.[2]

The phrase was in origin a dismissal of eclecticism, i.e. the "fear" is of the formidable intellectual opponent who has dedicated himself to and become a master in a single chosen discipline. In this first sense, the phrase was invoked by Methodist founder John Wesley to refer to himself, with "one book" (unius libri) taken to mean the Bible.[3] However, the phrase today most often refers to the interpretation of expressing "fear" of the opinions of the illiterate man who has "only read a single book".[4]


  1. ^ Jeremy Taylor, Life of Christ, Pt. II. Sect. II. Disc. II. 16.
  2. ^ Robert Southey, The Doctor, &c, (1848), Interchapter VII (e-text). 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).
  3. ^ "in 1730 I began to be homo unius libri, to study (comparatively) no book but the Bible." Letter to John Newton, May 14, 1765. 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!"
  4. ^ 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.
  • Eugene H. Ehrlich, Amo Amas Amat and More: How to use Latin to Your Own Advantage and the Astonishment of Others, p. 279. "An observation attributed to Aquinas"

External links[edit]

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