The article is an attempt to define reduction – a phenomenological methodological device – as the beginning of philosophy. The author considers such questions as: What motivates a phenomenologist to do reduction? Can one speak of philosophy before reduction? What is the essence of reduction? To answer these questions the author refers to Edmund Husserl and Jan Patočka, and tries to show that reduction is to be understood as an unmotivated expression of philosopher’s determination to overcome evidence inherent to natural attitude. The author argues that reduction enables one to perform a conceptualization of the world as such. Finally, reduction is defined as an attempt to take thinking seriously.