“The evil arising from mental improvement can be corrected only by a still further progress in that very improvement.”

Wen Jiabao (2008) cited in: Transcript of interview with Chinese Premier Wen Jiabao, 28 September 2008, CNN http://edition.cnn.com/2008/WORLD/asiapcf/09/29/chinese.premier.transcript/index.html,

Robert Henry Thurston, " The Growth of the Steam Engine https://books.google.nl/books?id=dywDAAAAMBAJ&pg=PA17," in: Popular Science, Nov 1877, p. 11

Source: The Theory of Political Economy (1871), Chapter I, Introduction, p. 44.
Context: A correct theory is the first step towards improvement, by showing what we need and what we might accomplish.

Source: An Essay on The Principle of Population (First Edition 1798, unrevised), Chapter IX, paragraph 8, lines 14-16

Essays, On Authorship and Style

Academy of Achievement interview (1991)
Context: I have come to associate a kind of success that we are referring to, to individuals who have a combination of attributes that are often associated with creativity. In a way they are mutants, they are different from others. And they follow their own drummer. We know what that means. And are we all like that? We are not like that. If you are, then it would be well to recognize that there were others before you. And, people like that are not very happy or content, until they are allowed to express, or they can express what's in them to express. It's that driving force that I think is like the process of evolution working on us, and in us, and with us, and through us. That's how we continue on, and will improve our lot in life, solve the problems that arise. Partly out of necessity, partly out of this drive to improve.

Introduction, in Hirst (1909), pp. 287–288
The National System of Political Economy (1841)

As quoted by John Ward, The lives of the professors of Gresham college (1740) p. 171. https://books.google.com/books?id=jp5bAAAAQAAJ&pg=PA171
Context: About this time, 1655, having an opportunity of acquainting myself with astronomy by the kindness of Dr. Ward, I apply'd myself to the improving of the pendulum for such observations, and in the year 1656, or 1657, I contriv'd a way to continue the motion of the pendulum, so much commended by Ricciolus in his Almagestum which Dr. Ward had recommended to me to peruse. I made some trials to this end, which I found to succeed to my wish. The success of these made me further think of improving it for finding the longitude; and the method I had made for myself for mechanick inventions, quickly led me to the use of springs, instead of gravity, for the making a body vibrate in any posture. Whereupon I did first in great, and afterwards in smaller modules, satisfy myself of the practicableness of such an invention; and hoping to have made great advantage thereby, I acquainted divers of my freinds, and particularly Mr. Boyle, that I was possessed of such an invention, and crav'd their assistance for improving the use of it to my advantage. Immediately after his majesty's restoration Mr. Boyle was pleased to acquaint the lord Brouncher and Sir with it, who advis'd me to get a patent for the invention, and propounded very probable ways of making considerable advantage by it. To induce them to a belief of my performance, I shewed a pocket watch, accommodated with a spring, apply'd to the arbor of the ballance, to regulate the motion thereof, concealing the way I had for finding the longitude. This was so well approv'd of, that Sir Robert Moray drew me up the form of a patent, the principal part whereof, viz. the description of the watch so regulated, is his own hand writing, which I have yet by me. The discouragement I met with in the management of this affair, made me desist for that time.