“The erasure of a human subspecies is largely painless — to us — if we know little enough about it. A dead Chinaman is of little import to us whose awareness of things Chinese is bounded by an occasional dish of chow mein. We grieve only for what we know. The erasure of Silphium from western Dane County is no cause for grief if one knows it only as a name in a botany book.”

Letter 17, 6.
Letters, Book VIII

Ramblings In Cheapside (1890)

Source: Lectures on Philosophy (1959), p. 90

Napoleon : In His Own Words (1916)

The First Part, Chapter 6, p. 24
Leviathan (1651)

First Mansions, Ch. 1, as translated by E. Allison Peers (1961) p. 18
Interior Castle (1577)
Context: It is no small pity, and should cause us no little shame, that, through our own fault, we do not understand ourselves, or know who we are. Would it not be a sign of great ignorance, my daughters, if a person were asked who he was, and could not say, and had no idea who his father or mother was, or from what country he came? Though that is a great stupidity, our own is incomparably greater if we make no attempt to discover what we are, and only know that we are living in these bodies and have a vague idea, because we have heard it, and because our faith tells us so, that we possess souls. As to what good qualities there may be in our souls, or who dwells within them, or how precious they are — those are things which seldom consider and so we trouble little about carefully preserving the soul's beauty. All our interest is centred in the rough setting of the diamond and in the outer wall of the castle – that is to say in these bodies of ours.

The Gift of Living With the Not Gifted http://www.wsj.com/articles/the-gift-of-living-with-the-not-gifted-1428103079 Wall Street Journal, April 3, 2015
From interviews and talks