The Japanese characters for Wa (和 harmony) and Jū (柔 softness / gentleness) are often seen as interchangeable, not least because they can both be pronounced as Yawara.

However, there does seem to be a fundamental difference between them

The Shinkage-ryū Tsuki no Shō (新陰流月之抄) written by Yagyū Jūbei Mitsuyoshi (柳生 十兵衛 三厳) in 1642, gives details of "Ryōi Shintō Wa" (良移心当和).

So, why use the term Wa (和) ?

In the 'Ryōi Shintō-ryū Denju Mokuroko’ (良移心当流 伝授 目録) 1623, Ryōi Shintō-ryū - Fukuno Shichirouemon Masakatsu (福野七郎右衛門正勝) explains the meaning of Ryōi Shintō wa as follows:

“The meaning of Ryōi Shintō wa is to shift (i 移) your heart (shin 心) well (ryō 良), then you will encounter (tō 当) harmony (wa 和)."

It seems that the principle of 'Wa' also encompassed a strategy, or guiding principle to Fukuno.

To my mind, harmony is not a fixed point between opposites, but rather a dynamic and harmonious balance which encompasses such opposites.

Fukuno also wrote:
"The hard/strong (剛) people know merely the hardness, while the weak (弱) people know only that they lack of force (力)...... Revolving the ten millions of (=infinite) schemes, consider the hardness as the father and the softness as the mother. "