“The unexamined life is not worth living” – Socrates

“We are what we repeatedly do. Excellence, then, is not an act, but a habit” – Aristotle

“Whereof one cannot speak, thereof one must be silent” – Ludwig Wittgenstein

“The life of man (in a state of nature) is solitary, poor, nasty, brutish, and short” – Thomas Hobbes

“History is Philosophy teaching by examples” – Thucydides

“I think therefore I am” (“Cogito, ergo sum”) – René Descartes

“He who thinks great thoughts, often makes great errors” – Martin Heidegger

“We live in the best of all possible worlds” – Gottfried Wilhelm Leibniz

“What is rational is actual and what is actual is rational” – G. W. F. Hegel

“God is dead! He remains dead! And we have killed him.” – Friedrich Nietzsche

“There is but one truly serious philosophical problem, and that is suicide” – Albert Camus

“One cannot step twice in the same river” – Heraclitus

In the same river, we both step and do not step, we are and we are not. Heraclitus (Fragment 49a)

What we saw and grasped, that we leave behind; but what we did not see and did not grasp, that we bring. Heraclitus (Fragment 56)

“The greatest happiness of the greatest number is the foundation of morals and legislation” – Jeremy Bentham

“To be is to be perceived” (“Esse est percipi”)– Bishop George Berkeley

“Happiness is not an ideal of reason but of imagination” – Immanuel Kant

"I've always wondered why meteorites land in craters."   - Sabine Hossenfelder

“No man's knowledge here can go beyond his experience” – John Locke

“God is not willing to do everything, and thus take away our free will and that share of glory which belongs to us” – Niccolo Machiavelli

“Liberty consists in doing what one desires” – John Stuart Mill

“It is undesirable to believe a proposition when there is no ground whatever for supposing it true” – Bertrand Russell

“The living are only a species of the dead, and a rare species at that.” Nietzsche