Dōgen often stressed the critical importance of zazen, or sitting meditation as the central practice of Buddhism. He considered zazen to be identical to studying Zen. This is pointed out clearly in the first sentence of the 1243 instruction manual ""Zazen-gi"" (坐禪儀; "Principles of Zazen"): "Studying Zen ... is zazen". Dōgen taught zazen to everyone, even for the laity, male or female and including all social classes. In referring to zazen, Dōgen is most often referring specifically to "shikantaza", roughly translatable as "nothing but precisely sitting", or "just sitting," which is a kind of sitting meditation in which the meditator sits "in a state of brightly alert attention that is free of thoughts, directed to no object, and attached to no particular content". In his "Fukan Zazengi", Dōgen wrote: