In martial arts they speak of hard and soft forces. An attack is a hard force; a defense redirecting the energy of such an attack is a soft force. In design, it's the sharp edge, straight line, spatial geometry, fine textures, and smooth surfaces that represent the hard forces. Yet, their visual energy can be redirected with even a slightest suggestion of a softening force.
Contrast makes oppositional forces even more acute. In the yin-yang that is life, where the two forces meet there is also harmony.
A master is fluent in both languages. S/he can effortlessly bring the two energies together into a balanced whole.
Harmony can be scaled in any direction: The balance needn't be centered.
Oppositional forces generate energy: Synergy.
Below, a rendering by Peter Guthrie of an imagined gallery at the Museo Canoviano, Possagno (Veneto, Italy).
Despite the dizzying spirals of yin-yang in color, texture, form, material, reflection, and opacity going on, the net effect is serene comfort.
Here, tenderness presented in what may be the ultimate example of soft power ever: The gift of forgiveness depicted in a hard and most unforgiving medium.
As if to extend the metaphor, there is the story of Lazlo Toth: Meeting Soft with Hard.
A couch, more or less: This from designer Shiro Kuramata in nickel-plated expanded metal mesh.