Gramsci, Antonio. "Culture and Ideological Hegemony." From Alexander, Jeffrey C., and Steven Seidman. Culture and Society: Contemporary Debates. Cambridge [England]: Cambridge University Press, 1990.
Everyone is a philosopher, says Gramsci, because 1. everyone uses language which is filled with deep meaning 2. everyone has more or less "common sense" and "good sense" and 3. everyone operates on a system of beliefs: religion, superstitions, opinions, etc. From there, Gramsci notes that humans construct their philosophy based on their particular social grouping, responding to the problems of their specific reality.
Gramsci comes to conclude that intellectual elites inevitably rise to organize their specific group sharing their philosophy because of their critical self-consciousness. This is how political parties form - leaders are chosen from among and by elites based on practical and theoretical criteria.