Practitioners know this and practice anyway because their experience has shown them phenomenal results. We don't have all the answers yet, and may never figure out every piece of the puzzle. This is part of the beauty, awe, and humility that is experienced by many practitioners and patients. Newton's theory in the 1600s described the human being as a divine type of mechanism or machine, with fixed parts, predictability, and alive within a closed system. But quantum physics of today describes us as fields within fields, as vibrating waves and particles, as equal to about 2 grains of sand in solid matter were we to be totally compressed.
Thought is a form of energy.
These statements directly relate to the intentionality that an energetic practitioner uses during treatments. Spirituality and science have been kept separate since the scientific era, but more and more we are seeing the holism of all creation, the connectedness of everyone and everything, and the re-emergence of science and spirituality as different perspectives of the same thing. Studies on the existence of energy fields and the effects of energetic therapy have been published regularly since the early 1960s. Ancient text of major cultures refer to the energy system. I heartily implore anyone who is either against the use of energetic therapy or uninformed about it, to explore it open-mindedly and fairly.