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“The happiness of your life depends upon the quality of your thoughts.”
The line emphasizes the role of habitual judgment in shaping lived experience, a recurring theme in Stoic practice.
Source note: Common English rendering of a passage in Meditations; wording varies by translation.
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“A long habit of not thinking a thing wrong, gives it a superficial appearance of being right.”
Custom can disguise error by making the familiar feel legitimate; critical judgment requires re-examining practices that have escaped scrutiny through repetition.
Source note: Common Sense, Introduction; Paine uses the observation to explain the resistance that unfamiliar political arguments may initially provoke.
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“To define is to limit.”
Voice: Fictional character · Lord Henry Wotton
Definitions clarify ideas but can also narrow them, especially when a label is treated as the complete reality of a person or experience.
Source note: The Picture of Dorian Gray, 1891 edition, Chapter 17; Lord Henry answers the Duchess of Monmouth’s question “What are you?” with “To define is to limit.”
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“The universe is wider than our views of it.”
Reality exceeds any one viewpoint, so confidence in a perspective should leave room for what has not yet been seen.
Source note: Walden, Conclusion; Thoreau uses the sentence while arguing that familiar human views do not exhaust reality.
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“There is nothing either good or bad, but thinking makes it so.”
Voice: Fictional character · Hamlet
The line separates events from the judgments people place on them, a useful distinction for thinking about perception and response.
Source note: Hamlet, Act 2, Scene 2; Hamlet says this to Rosencrantz and Guildenstern while explaining that Denmark feels like a prison to him. The line is dramatic dialogue, not a detached psychological proposition by Shakespeare.
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“He who knows only his own side of the case, knows little of that.”
Understanding a position requires serious contact with competing arguments; familiarity with only one side can produce confidence without real comprehension.
Source note: On Liberty, Chapter 2; Mill argues for open discussion because opposing views expose weaknesses and sharpen understanding.