A significant foundational element of all Nightengale's individual tenets is that nursing is separate and distinct from medical practice. She theorized that, while educational background was indeed necessary (an idea honored from the time she expressed it), the nurse's job was to provide intervention between physical and psychological impediments (e.g., loud noise) to healing and the body's ability to call upon inner resources to produce healing given optimal medical care and circumstances. The underlying paradigm of Nightingale's theory is that disease is literally lack of ease; it is the lack of ease that greatly impedes recovery in optimal conditions. For this reason, observation was as important as cleanliness and giving hope as important as food and light. These abstract elements that separate nursing from medical care are what seems to be lacking from doctor's office and hospital nursing in the contemporary age.
One important idea was the proper training of nurses as medical professionals, not just assistant to doctors without medical knowledge of their own. Although she considered doctors to be of a different field than nurses, Nightingale wanted nurses to have real medical knowledge that they could use, both to give better care to their patients, and for emergencies when doctors were overwhelmed with work. She advocated better education and training for women in general and nurses in particular, and often met with nursing students in person after they graduated. This focus on education helped the overall woman's rights movement, and allowed more women to become valued members of society (insofar as they had skills that were deemed vital) rather than invisible workers without real knowledge or ability.
To me, the most important tenant of Florence Nightingale’s philosophy is the importance of professionalism in nursing.
She also advocated strict discipline, an attention to cleanliness, and felt that nurses should possess an innate empathy for their patients. (enotes)
The attention to detail is amazing. She was aware of the need for cleanliness at a time when most people were not really thinking that way.
The very first requirement in a hospital is that it should do the sick no harm. (brainyquote)
I think this is a very important idea, not the least because I am deathly afraid of hospitals. It seems like you would not need to suggest that hospitals should not make people sick, but that is easier said than done.
Florence Nightingale also believed that nurses should have empathy for their patients. I would say this is just as important today as it was then.
I would say that the most important tenet of Florence Nightingale’s theory was the idea that the patient’s environment had a great deal to do with whether the patient would be able to get better. Nightingale believed that patients needed a good environment in which to recover and that nurses needed to help make this happen. She argued that patients needed things like good light and fresh air. She felt they needed sufficient food and clean water to drink.
For Nightingale, the role of the nurse was to create these sorts of conditions that would allow the patient to heal. The nurse was not there to practice medicine but to create an environment conducive to healing.