Verifiability
There are now studies which allow us to see the effects which LichtWesen products have. For example, a camera from Auramed can reveal how our aura changes within minutes of spraying an essence or putting on a crystal. Applied kinesiology, Kirlian photos, EAV (electroacupuncture according to Voll) and blind tests also show this.
Nonetheless, it is your own experience which is decisive, so we advise: trust your own critical perception when using the products.
Here you can find a test of an essence at the Life-Test Institute.