“[A]ll disease, at some period or other of its course, is more or less a reparative process, not necessarily accompanied with suffering: an effort of nature to remedy a process of poisoning or of decay […].”

Here, Nightingale lays down the basic principle that health is a natural process and that illness is the body’s reaction to a foreign obstacle. What would typically be considered sickness—a fever, for example—is the body’s process of healing. The symptoms of illness are evidence that an illness or foreign substance is harming the body and aren't themselves necessarily bad or harmful.

“I use the word nursing for want of a better. It has been limited to signify little more than the administration of medicines and the application of poultices. It ought to signify the proper use of fresh air, light, warmth, cleanliness, quiet, and the proper selection and administration of diet—all at the least expense of vital power to the patient.”

This passage gives a baseline definition of nursing that is more inclusive and holistic than typically thought. While many consider nursing the administration of medicine and supplemental care, Nightingale argues that nursing is primarily an art of creating the proper conditions for the human body to heal and flourish. Fresh air, light, and sanitation are all the proper concern of the nurse because they relate to the patient's health, and the patient can't be restored to proper health without these necessities of human life.

“How much sickness, death, and misery are produced by the present state of many factories, warehouses, workshops, and workrooms!”

Here, as in many other places, Nightingale emphasizes that illness isn't a mystery but an expected result of (in many instances) the environment. The poor conditions of many factories and places of industry directly and unnecessarily contributed to the poor