Demosthenes should be a perfect master both of the narrated facts, and of the sagacious theorisings of Thucydides in those facts, we may take for granted.  And, farther, the orations delivered by opposing speakers in the great critical debates, might very well have been committed verbatim by a young orator; many of them are masterpieces of oratory in every point of view.  But the reason for getting them by heart does not apply to the general narrative.  Even to imbibe the best qualities of the style of Thucydides would not require whole pages to be learnt verbatim; a much better way would readily occur to any intelligent man.

In fact, there is no case where it is profitable to load the memory with a whole book, or with large portions of a book.  There are many small portions of every leading work that might be committed with advantage.  Principal propositions ought to be retained to the letter.  Passages, here and there, remarkable for compact force, for argumentative power, or elegant diction, might be read and re-read till they clung to the memory; but this should be the consummation of a thorough and critical estimate of their merits.  To commit to memory without thinking of the meaning is a senseless act; and could not be ascribed to Demosthenes.  At the stage when the young student is forming a style, he is assisted by laying up memoriter a number of passages of great authors; but it is never necessary to go beyond select paragraphs.  Detached sentences are valuable, and strain the memory least.  Entire paragraphs have a farther value in impressing good paragraph connection; but, to string a number of paragraphs together, or to learn whole chapters by memory, has nothing to recommend it in the way of mental culture.

There is a memory in extension that holds a long string of words and ideas together.  Its value is to get readily at anything occurring in a certain train, as in a given book.  It is the memory of easy reference.  There is also a memory of intension, that takes a strong grasp of brief expressions and thoughts, and brings them out for use, on the slightest relevancy.  The two modes interfere with each other’s development; we cannot be great in both; while, for original force, the second is worth the most:  it extracts and resets gems to tesselate our future structures; it constitutes depth as against fluency.

To commit poetical passages to memory is a valuable contribution to our stock of material for emotional resuscitation in after years.  It also aids in adorning our style, even although we may not aspire to compose in poetry.  But the burden of holding the connection of a long poem should be eschewed.  Children can readily learn a short psalm or hymn, and can retain it in permanence; but to repeat the 119th psalm from the beginning is the mere tour-de-force of a strong natural memory, and a waste of power; just as much as committing an entire book of the Aeneid or of Paradise Lost.