“What I mean (and everybody else means) by the word ‘quality’ cannot be broken down into subjects and predicates. This is not because Quality is so mysterious but because Quality is so simple, immediate and direct.”

Source: Quality Control: Principles, Practice, and Administration. 1951, p. 1

Source: The Blood of Olympus

As quoted in "Vertex Interviews Philip K. Dick" by Arthur Byron Cover, in Vertex, Vol. 1, no. 6 (February 1974) http://2010philipkdickfans.philipkdickfans.com/frank/vertexin.htm
Context: I started reading SF when I was about twelve and I read all I could, so any author who was writing about that time, I read. But there's no doubt who got me off originally and that was A. E. van Vogt. There was in van Vogt's writing a mysterious quality, and this was especially true in The World of Null A. All the parts of that book did not add up; all the ingredients did not make a coherency. Now some people are put off by that. They think that's sloppy and wrong, but the thing that fascinated me so much was that this resembled reality more than anybody else's writing inside or outside science fiction. … reality really is a mess, and yet it's exciting. The basic thing is, how frightened are you of chaos? And how happy are you with order? Van Vogt influenced me so much because he made me appreciate a mysterious chaotic quality in the universe which is not to be feared.

Lecture II : The Universal Categories, § 1 : Presentness, CP 5.44
Pragmatism and Pragmaticism (1903)
Context: The quality of feeling is the true psychical representative of the first category of the immediate as it is in its immediacy, of the present in its direct positive presentness. Qualities of feeling show myriad-fold variety, far beyond what the psychologists admit. This variety however is in them only insofar as they are compared and gathered into collections. But as they are in their presentness, each is sole and unique; and all the others are absolute nothingness to it — or rather much less than nothingness, for not even a recognition as absent things or as fictions is accorded to them. The first category, then, is Quality of Feeling, or whatever is such as it is positively and regardless of aught else.

1946 - 1963, interview with John Richardson' (1957)

As quoted in How They Succeeded (1901) by Orison Swett Marden
Context: I do not think that there is any other quality so essential to success of any kind as the quality of perseverance. It overcomes almost everything, even nature.

Source: Quality Control: Principles, Practice, and Administration. 1951, p. vii; Preface: lead paragraph