First of all, I would like to thank to the Universidad Panamericana, especially to the Instituto de Humanidades. In this regard, we would like to thank in particular Alberto Ross, Nicolás Esparza and Nassim Bravo, also Mariana Herrera and Maria Asunción Lira González. Their constant motivation and support have been fundamental to complete my work. I am grateful with Jon Stewart for his advice and constant support. I am deeply grateful to my brother, Ernesto Esparza, for giving me the Ernst Cassirer Gesammelte Werke; they were essential to completing this work, and I consider his gift a true gesture of brotherhood.
Finally, I would like to thank my wife, Ana, for guiding me in my work and for encouraging me to follow a philosophical way of life.