“To study and not think is a waste. To think and not study is dangerous.”
Variant: Learning without reflection is a waste, reflection without learning is dangerous.
Source: The Analects, Chapter II
Original
學而不思則罔,思而不學則殆。
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Confucius 269
Chinese teacher, editor, politician, and philosopher -551–-479 BCRelated quotes
Source: Darwin, God and the Meaning of Life: How Evolutionary Theory Undermines Everything You Think You Know (2010), p. 256

Source: Primer of scientific management, 1912, p. 8

Pond, Steve. "'Silver Linings Playbook' Oscar Nominee Jennifer Lawrence Shares Her Acting Secret: Never Sweat" https://movies.yahoo.com/news/silver-linings-playbook-oscar-nominee-jennifer-lawrence-shares-220811334.html. movies.yahoo.com. February 15, 2013. Retrieved March 29, 2014.

1880s, 1884
Source: Quote from Letter 355, from Nuenen The Netherlands, January 1884; as quoted in Vincent van Gogh, edited by Alfred H. Barr; Museum of Modern Art, New York, 1935 https://www.moma.org/documents/moma_catalogue_1996_300061887.pdf, page: Catalog: Dutch Period 2. - Weaver
Preface
Maynard Keynes: An Economists' Biography (1992)
Homage to the square' (1964), Oral history interview with Josef Albers' (1968)
Philosophy : the basics (Fifth Edition, 2013), Introduction

Quoted by Bishop Jean-Pierre Camus in The Spirit of Saint Francis de Sales, ch. 1, Pg. 3 (1880)