“Vertical thinking is selection by exclusion. One works within a frame of reference and throws out what is not relevant. With lateral thinking one realizes that a pattern cannot be restructured from within itself but only as the result of some outside influence.”

Source: Lateral Thinking : Creativity Step by Step (1970), p. 29.
Context: Rightness is what matters in vertical thinking. Richness is what matters in lateral thinking. Vertical thinking selects a pathway by excluding other pathways. Lateral thinking does not select but seeks to open up other pathways. With vertical thinking one selects the most promising approach to a problem, the best way of looking at a situation. With lateral thinking one generates as many alternative approaches as one can.

Rolling Stone interview (1968)

Ch 3 : Creativity and the Unconcious, p. 59
The Courage to Create (1975)
Context: A dynamic struggle goes on within a person between what he or she consciously thinks on the one hand and, on the other, some insight, some perspective that is struggling to be born. The insight is then born with anxiety, guilt, and the joy and gratification that is inseparable from the actualizing of a new idea or vision.

Source: Lateral Thinking : Creativity Step by Step (1970), p. 5; Preface.
Context: Lateral thinking... is the process of using information to bring about creativity and insight restructuring. Lateral thinking can be learned, practised and used. It is possible to acquire skill in it just as it is possible to acquire skill in mathematics.

Source: Lateral Thinking : Creativity Step by Step (1970), p. 159.
Context: The concept of lateral thinking is insight restructuring and this is brought about through the rearrangement of information. Rearrangement is the basis of lateral thinking and rearrangement means escape from the rigid patterns established by experience. The rearrangement process is incorporated in the concept of the (re) laxative. The laxative is a rearranging device. It is the means whereby one can escape from established patterns and create new ones. The laxative allows the arrangement of information in new ways from which new patterns can arise. The concept of the laxative is crystallized into a definite language tool. This language tool is PO. Once one learns the function and use of PO one has learned how to use lateral thinking. The whole concept of lateral thinking is concentrated in the use of this language tool. Lateral thinking could be said to be the management of PO just as logical thinking is the management of NO.

Vol. VI, p 5, "First Talk in Rajahmundry (20 November 1949) http://www.jkrishnamurti.com/krishnamurti-teachings/view-text.php?tid=335&chid=4655&w=%22You+cannot+find+truth+through+anybody+else%22, J.Krishnamurti Online, JKO Serial No. 491120
Posthumous publications, The Collected Works
Context: You cannot find truth through anybody else. How can you? Surely, truth is not something static; it has no fixed abode; it is not an end, a goal. On the contrary, it is living, dynamic, alert, alive. How can it be an end? If truth is a fixed point, it is no longer truth; it is then a mere opinion. Sir, truth is the unknown, and a mind that is seeking truth will never find it. For mind is made up of the known; it is the result of the past, the outcome of time — which you can observe for yourself. Mind is the instrument of the known; hence it cannot find the unknown; it can only move from the known to the known. When the mind seeks truth, the truth it has read about in books, that "truth" is self-projected, for then the mind is merely in pursuit of the known, a more satisfactory known than the previous one. When the mind seeks truth, it is seeking its own self-projection, not truth. After all, an ideal is self-projected; it is fictitious, unreal. What is real is what is, not the opposite. But a mind that is seeking reality, seeking God, is seeking the known. When you think of God, your God is the projection of your own thought, the result of social influences. You can think only of the known; you cannot think of the unknown, you cannot concentrate on truth. The moment you think of the unknown, it is merely the self-projected known. So, God or truth cannot be thought about. If you think about it, it is not truth. Truth cannot be sought; it comes to you. You can go after only what is known. When the mind is not tortured by the known, by the effects of the known, then only can truth reveal itself. Truth is in every leaf, every tear; it is to be known from moment to moment. No one can lead you to truth; and if anyone leads you, it can only be to the known.

Darwin's first published expression of the concept of natural selection.
"On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection" Journal of the Proceedings of the Linnean Society of London: Zoology (read 1 July 1853; published 20 August 1858) volume 3, pages 45-62, at page 51 http://darwin-online.org.uk/content/frameset?pageseq=7&itemID=F350&viewtype=image
Other letters, notebooks, journal articles, recollected statements

Michael Witzel – An Examination of his Review of my Book (2001)

The Basic Teachings - Part 1: Principles of the Teaching (2009)