In the first (passive) sense saṅkhāra can refer to any compound form in the Universe whether a tree, a cloud, a human being, a thought or a molecule. All these are saṅkhāras. The Buddha taught that all such things are inconstant, arising and passing away, subject to change and that knowing this, not in a rational, but empirical manner, is wisdom. Saṅkhāra is often used in this first sense to describe the psychological conditioning (particularly the habit patterns of the unconscious mind) that gives any individual human being his or her unique character and make-up at any given time.