I doubt about everything, even…

Doubt grows with knowledge.

–Johann Wolfgang von Goethe (1749 – 1832)

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To know much is often the cause of doubting more.

–Michel de Montaigne (1533 – 1592)

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To have doubted one’s own first principles is the mark of a civilized man.

–Oliver Wendell Holmes Jr. (1841 – 1935)

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Doubt everything. Find your own light.

–Buddha (c. 5th century BCE)

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Doubt whom you will, but never yourself.

–Christian Nestell Bovee (1820 – 1904)

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When we are in love we often doubt that which we most believe.

–François de La Rochefoucauld (1613 – 1680)

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Doubt is a pain too lonely to know that faith is his twin brother.

–Khalil Gibran (1883 – 1931)

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The deplorable mania of doubt exhausts me. I doubt about everything, even my doubts.

–Gustave Flaubert (1821 – 1880)

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Doubt everything or believe everything: these are two equally convenient strategies. With either we dispense with the need for reflection.

–Henri Poincaré (1854 – 1912)

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Your doubt can become a good quality if you train it. It must become knowing, it must become criticism.

–Rainer Maria Rilke (1875 – 1926)