A simple collection of notes from Discourse on the Method by Descartes:

• "For to be possessed of good mental powers is not sufficient; the principal matter is to apply them well. The greatest minds are capable of the greatest vices as well as of the greatest virtues, and those who proceed very slowly may, provided they always follow the straight road, really advance much faster than those who, though they run, forsake it." [1, p. 2]
• One should contain reform efforts to their own person. To do otherwise invites too many unintended or harmful consequences. Each person in turn must decide for themselves what reforms are required. [1, p. 12 - 13]
• Four step method to attain knowledge:
  1. Accept as true only that for which you are certain [1, p. 16]
  2. Break complex ideas down into many simpler ideas [1, p. 17]
  3. Understand simple ideas before more complex ones [1, p. 17]
  4. Never leave out any detail or consequence [1, p. 17]
• Basic code of ethics:
  1. In matters where one hasn't developed personal opinions, for there is always more to consider than there is time, live by the most moderate codes of conduct for the land one lives in. Life long commitments, such as marriage or religious vows, are always considered to be extreme even if common.
  2. When once having come to a conclusion on a course of actions, follow that conclusion to its end. In this way, while one may go in a wrong direction, at least the error will be made clear over time instead of nothing being clarified by jerking one way to the next in fits of doubt.
  3. Seek first to change myself rather than the world around me. My power to change the world is limited while my power to change my thoughts is complete, if not easy. After doing my best to alter the world to my liking what is left to me is to change myself to find contentment with the outcome.

References

[1] Eaton, Ralph M., ed. Descartes Selections. USA: Charles Scribner's Sons, 1927.