From: http://www.judoamerica.com/coaches/kano-kata.shtml

In passing, Gleeson introduces Shao's cosmological structure, making a point of the dichotomy of the static universe into ju (soft) and go (hard) elements. Historically, from the martial arts perspective, this turned out to be less important than the holistic mind-body relationship emphasized by Shao's successor Wang Yang Ming, especially his notion of ju as making the body "soft" or "pliant" to the will 5. This concept was one of the many
faces of ju perceived and embraced by Kano. Gleeson makes this allusion, but never offers these details, and to the extent that it does succeed, it misleads. Having introduced the subject, Gleeson fails to offer more critical, more relevant information from Kano's own martial arts lineage. So the reader is left with a shaded, incomplete picture.

Kano extensively studied the Tenjin Shinyo Ryu Jujutsu which is a fusion of Shin no Shindo Ryu and Yoshin Ryu. Yoshin Ryu (Yo, meaning "willow tree,"and Shin, meaning "heart or spirit") was de-vised by a doctor from Nagasaki named Shirobei Yoshitoki Akiyama. Akiyama had studied battlefield and healing arts in Japan, and is thought to have been accomplished in Jujutsu.
Wishing to extend his knowl-edge, Akiyama went to China to study in the 1600s. There he studied medicine, katsu (life-restoring tech-niques), and various martial arts, especially striking arts and their use as applied to vital areas (kyusho-jutsu). He also studied Taoism, Taoist healing and martial arts, and acu-punc-ture. The centerpiece of the art he created by incorpor-ating his training in China with Japanese methods was a syllabus of 300 techniques. This represented an infusion of the "soft" or "internal" martial arts of China into Japan 6.

The soft or internal arts were known popularly in China as jou-chuan, the characters for which are read in Japanese as "ju-ken," meaning "soft fist." It was common throughout that period to refer to all internal arts by this name. This may have played some role in the eventual popularity of the term jujutsu for these rough-and-tumble martial arts. Kano and others argued that there was nothing "gentle" or "soft" about Jujutsu, and that ju was hardly
the over-riding principle of the arts.The arts were called "ju-arts" or jujutsu because they were based on internal methods and ki (internal energy), not because they employed no strength or force 7.