In 1628 or perhaps a few years earlier, the rationalist Ren Descartes (1596 - 1650) began work on a treatise, left unfinished, regarding the correct method for scientific and philosophical thinking, entitled: 'Regulae ad directionem ingenii', or 'Rules for the Direction of the Mind'. To honor his effort, this little book brings together hundred rules covering the game of knowing. This sport, played by scientists and philosophers alike, intends to gather novel conceptual knowledge (context of discovery) valid pro tem (context of justification).