The world is a book, and those who do not leave home read but one page.

Augustine of Hippo (354-430) Christian church father, philosopher, saint [b. Aurelius Augustinus]
(Spurious)

This quotation, and variants, are widely attributed to Augustine, but, though he did on occasion write of the world as a a text or book, it was not in the sense of encouraging travel (which Augustine did not like), but in the sense that anyone could read the message of God in the world around them, even if they could not read Scripture itself. For example in Exposition of the Psalms [Enarrationes in Psalmos] on Psalm 45, sec. 7 (v. 4), he writes:

The page of divine scripture is open for you to read, and the wide world is open for you to see. Only the literate can read the books, but even the illiterate can read the book of the world.
[tr. Boulding (2000)]
 
May the sacred page be a book for you, so that you may hear, may the globe of the earth be a book for you, so that you may see; in these books only those who know letters read these things; in the whole world, even the fool can read.
[tr. Mews (2004)]
 
[Liber tibi sit pagina diuina, ut haec audias; liber tibi sit orbis terrarum, ut haec uideas. in istis codicibus non ea legunt, nisi qui litteras nouerunt; in toto mundo legat et idiota.]

If this was the source of the original quote -- which begins to show up in English in the late 18th Century -- it was significantly distorted. Early appearances of the version we know today:

The world is a great book, and none study this book so much as a traveler. They that never stir from their home read only one page of this book.
[ed. Feltham, The English Enchiridion (1799), paraphrasing]

The world is a great book, of which they that never stir from home read only a page.
[ed. Fiedling, Select Proverbs of All Nations (1824)]

It is in turn possible that Augustine's "world is a book" metaphor was somehow conflated with this original expression in Fougeret de Monbron, Le Cosmopolite (opening words) (1750):

The universe is a sort of book, whose first page one has read when one has seen only one's own country.
 
[L'Univers est une espece de livre dont on n'a lû que la prémiére page, quand on n'a vû que son Païs.]

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