The wise men differed from others in three matters: excellence in knowledge, monopolization of it, and formulation of it. Theoretical knowledge has a bumpy road, with continuous contemplation, extracting thought, deducing general rules from observations and experiences, then applying the rule to determine its validity, and correcting it if an error is discovered. Which requires a long time that may not be measured by the lifespan of an individual, but rather by the lifespan of generations and generations. The science and knowledge that humanity has achieved today is the fruit of all humanity since the dawn of civilization. It is the history of human thought, which has passed - and continues to pass - two stages, a stage of monopoly and a stage of permissibility. The establishment of philosophical schools arose in a relatively late era in the history of human civilization, which can be roughly defined as the sixth century BC in terms of time, and in Greece in terms of place. Philosophical schools did not stop at analyzing social systems and trying to understand them except to work on drawing new lines for a better society by inventing new systems that work to develop and promote society. There is ample space in this book to talk about some philosophical schools, especially the major ones, and what was closely related to Arab civilization, with care being taken to mention the Arab philosophical schools that are part of our heritage.