In the Soto school of Zen, meditation with no objects, anchors, or content, is the primary form of practice. The meditator strives to be aware of the stream of thoughts, allowing them to arise and pass away without interference. Considerable textual, philosophical, and phenomenological justification of this practice can be found throughout Dōgen's Shōbōgenzō, as for example in the "Principles of Zazen"[web 14] and the "Universally Recommended Instructions for Zazen".