The quote "Let us study things that are no more. It is necessary to understand them, if only to avoi…" is famous quote by Victor Hugo (1802–1885), French poet, novelist, and dramatist.
Source: Les Misérables
Un Art de Vivre (The Art of Living) (1939), The Art of Working
“Let thy understanding enter into the things that are doing and the things which do them.”
VII, 30
Meditations (c. 121–180 AD), Book VII
Context: Direct thy attention to what is said. Let thy understanding enter into the things that are doing and the things which do them.
Book VIII 1337b.5 http://books.google.com/books?id=ZrDWAAAAMAAJ&pg=PA245&dq=%22absorb+and+degrade+the+mind%22&hl=en&sa=X&ei=c6NaUbatEYWp4AOWp4CoBA&ved=0CHYQ6AEwDA#v=onepage&q=%22absorb%20and%20degrade%20the%20mind%22&f=false, 1885 edition
Politics
Context: There can be no doubt that children should be taught those useful things which are really necessary, but not all things, for occupations are divided into liberal and illiberal; and to young children should be imparted only such kinds of knowledge as will be useful to them without vulgarizing them. And any occupation, art, or science which makes the body, or soul, or mind of the freeman less fit for the practice or exercise of virtue is vulgar; wherefore we call those arts vulgar which tend to deform the body, and likewise all paid employments, for they absorb and degrade the mind. There are also some liberal arts quite proper for a freeman to acquire, but only in a certain degree, and if he attend to them too closely, in order to attain perfection in them, the same evil effects will follow.
“The only thing necessary is to understand attachment”
Everyday Peace: Letters for Life, 2000
Context: You have everything and you want more. It's natural in human beings. You don't need to give away your house, money, and car, and leave your family to find God. The only thing necessary is to understand attachment. (p.17)
The Art of Persuasion
Context: Whilst in speaking of human things, we say that it is necessary to know them before we can love them... the saints on the contrary say in speaking of divine things that it is necessary to love them in order to know them, and that we only enter truth through charity.
Source: My Best Friend's Girl
Book VII : Modern Times, Ch. IX : The Final Consequences
Penguin Island (1908)
Context: Penguinia gloried in its wealth. Those who produced the things necessary for life, wanted them; those who did not produce them had more than enough. "But these," as a member of the Institute said, "are necessary economic fatalities." The great Penguin people had no longer either traditions, intellectual culture, or arts. The progress of civilisation manifested itself among them by murderous industry, infamous speculation, and hideous luxury. Its capital assumed, as did all the great cities of the time, a cosmopolitan and financial character. An immense and regular ugliness reigned within it. The country enjoyed perfect tranquillity. It had reached its zenith.
Reflections on Various Subjects (1665–1678), V. On Conversation
