“At bottom there is but one subject of study: the forms and metamorphoses of mind. All other subjects may be reduced to that; all other studies bring us back to this study.”

Source: Introduction to General Systems Thinking, 1975, p. 30; Quote in: Dieter Spath, Walter Ganz (2008) The Future of Services: Trends and Perspectives. p. 226

Editor's Introduction, The Teaching of Elementary Mathematics https://books.google.com/books?id=NKoAAAAAMAAJ (1906) by David Eugene Smith

David Eugene Smith, "Editor's Introduction," in: The Teaching of Elementary Mathematics https://books.google.com/books?id=NKoAAAAAMAAJ (1906)

Letter to Abigail Adams (12 May 1780)
1780s
Context: The science of government it is my duty to study, more than all other sciences; the arts of legislation and administration and negotiation ought to take the place of, indeed exclude, in a manner, all other arts. I must study politics and war, that our sons may have liberty to study mathematics and philosophy. Our sons ought to study mathematics and philosophy, geography, natural history and naval architecture, navigation, commerce and agriculture in order to give their children a right to study painting, poetry, music, architecture, statuary, tapestry and porcelain.

[The Value of Useless Studies, Nature, 25 February 1892, https://babel.hathitrust.org/cgi/pt?id=pst.000047662452;view=1up;seq=433] (p. 392)

Global Ideas from Pluto's Challenger (May 21, 2009)
Context: The best educators are the ones that inspire their students. That inspiration comes from a passion that teachers have for the subject they're teaching. Most commonly, that person spent their lives studying that subject, and they bring an infectious enthusiasm to the audience.I think many people have that enthusiasm, but they are prevented from being teachers because they didn't go through the teacher mill. Now you have teachers who have been through the teacher mill, yet they have no capacity to inspire anyone at all. It's the inspired student that continues to learn on their own. That's what separates the real achievers in the world from those who pedal along, finishing assignments.

Source: The New Industrial State (1967), Chapter X, Section 5, p. 122 (Mr. Galbraith was originally an agricultural economist...)

Source: Money: Whence It Came, Where It Went (1975), Chapter I, Money, p. 5

Source: "The Scientific Character of Geology," 1961, p. 453; quoted in: Robert Woodtli (1964), Methods of Prospection for Chromite, p. 80