“Denken tut weh” (Thinking hurts)
— Georg Simmel

“The history of thought is the history of its models.”
— Fredric Jameson, The Prison-House of Language

“Something is happening to the way we think about the way we think.”
— Clifford Geertz, “Blurred Genres: the Refiguration of Social Thought”

“I am convinced that there are ways of thinking that we don’t yet know about.”
— Adrienne Rich

“Thinking, like life, is never complete, it is a possibility that never exhausts itself.”
— Vincenzo Di Nicola

“All that we are is the result of our thoughts; it is founded on our thoughts and made up of our thoughts. With our thoughts we make the world. If a man speaks or acts with a harmful thought, trouble follows him as the wheel follows the ox that draws the cart.”
— The Dhammapada

“Writing is thinking. That means that you won’t think unless you do it.”
— Sarah Beckwith

“We come to know what it means to think when we ourselves try to think.”
— Martin Heidegger, What is Thinking?

“Preoccupation with philosophy more than anything else may give us the stubborn illusion that we are thinking just because we are incessantly ‘philosophizing.'”
— Martin Heidegger, What is Thinking?

“The question whether objective truth can be attributed to human thinking is not a question of theory but is a practical question. Man must prove the truth — i.e. the reality and power, the this-sidedness of his thinking in practice. The dispute over the reality or non-reality of thinking that is isolated from practice is a purely scholastic question.”
— Karl Marx, Theses on Feuerbach

“Feuerbach, not satisfied with abstract thinking, wants contemplation; but he does not conceive sensuousness as practical, human-sensuous activity.”
— Karl Marx, Theses on Feuerbach