Human digestive system digestive system is subject to a wide range of disorders many of which can be congenital. Mouth diseases can also be caused by pathogenic bacteria, viruses, fungi and as a side effect of some medications. Mouth diseases include tongue diseases and salivary gland diseases. A common gum disease in the mouth is gingivitis which is caused by bacteria in plaque. The most common viral infection of the mouth is gingivostomatitis caused by herpes simplex. A common fungal infection is candidiasis commonly known as "thrush" which affects the mucous membranes of the mouth. There are a number of esophageal diseases such
A Treatise of Human Nature working assumption that nature tends to produce variety from "a few principles", he hopes to find "general principles" underlying our moral psychology. Second, to the question of whether these principles are "natural", he replies that it depends on the meaning of "natural": they are not "miraculous", nor are they "rare", but they might sometimes draw on human "artifice" (his system will include both natural virtues and artificial virtues), adding that none of these meanings can sustain the popular view (defended by Butler) that "virtue is the same with what is natural, and vice with what is unnatural". Before proceeding to