Common Sense

I can't give just one, but here are a few that had a strong influence on me: "12 Rules for Life" by Jordan Peterson, "Why Switzerland?" Jonathan Steinberg, "Little Book of Common Sense Investing" by John C. Bogle, "A Random Walk Down Wall Street" by Butron Malkiel, "Liberalismus" by Ludwig von Mises, "Meditations" by Marcus Aurelius, "A Treatise of Human Nature" by David Hume, "Thinking, Fast and Slow" by Daniel Kahneman, "The Law" by Frédéric Bastiat, "Autobiography" by Benjamin Franklin, "Common Sense" by Thomas Paine, "Gespräche mit Goethe" by Johann Peter Eckermann, "Walden" by Henry David Thoreau, "The Old Regime and the Revolution" Alexis de Tocqueville, "On Liberty" by John Stuart Mill, "A Treatise on Political Economy" by Jean-Baptiste Say, "The Man Versus the State" by Herbert Spencer, "The Revolt of the Masses" by José Ortega y Gasset, "Capitalism, Socialism and Democracy" by Joseph Alois Schumpeter, "The Logic of Scientific Discovery" by Karl Popper, "The Machinery of Freedom" by David Friedman, "On Power" Bertrand de Jouvenel, "1984" by George Orwell, "The State" by Anthony de Jasay, "Sketched With the Quill" by Andrzej Bobkowski, "My Correct Views on Everything" by…

"I'm wondering which other books have you read that have had the most impact on you professionally or even personally?" Professionally: Peter F. Drucker's books. Personally: "Meditations" by Marcus Aurelius, "A Treatise of Human Nature" by David Hume, "The Law" by Frédéric Bastiat, "Autobiography" by Benjamin Franklin, "Common Sense" by Thomas Paine, "Gespräche mit Goethe" by Johann Peter Eckermann, "The Old Regime and the Revolution" Alexis de Tocqueville, "On Liberty" by John Stuart Mill, "The Man Versus the State" by Herbert Spencer, "The Revolt of the Masses" by José Ortega y Gasset, "The Logic of Scientific Discovery" by Karl Popper, "On Power" Bertrand de Jouvenel, "1984" by George Orwell, "The State" by Anthony de Jasay, "Sketched With the Quill" by Andrzej Bobkowski, "Metaphysical Horror" by Leszek Kolakowski, "Rationality in Economics" by Vernon L. Smith, "The Machinery of Freedom" by David Friedman.

I think the quality of advice you're getting on this thread is very mixed. Some of the books mentioned are absolutely great-- like "Being and Time", or Husserl's "Logical Investigations"-- but incredibly difficult to read unprepared. If you were ready to be reading them, you wouldn't be asking the question here. The two books you mention in the question (Common Sense and "On the Fourfold Root") are both quite readable, as are a few of the primary texts mentioned in the responses ("Existentialism is a Humanism", "Thus Spoke Zarathustra") but in general, I'd have to suggest you stay away from primary texts at first. In other words, begin by reading works about philosophy, rather than works of philosophy. A single-volume work on the history of philosophy will give you the broad scope (for example, Durant, or Russell, or "Sophie's World" if you prefer fiction), but will tend to turn the philosophers discussed into caricatures of themselves. You mention that you are in school; I'd suggest you take a philosophy course or two, if you are interested in the field. Having an experienced guide will definitely help.