Understanding our individual constitution, as we have seen, is one of the main ways of keeping good health. Diseases, according to Ayurveda are caused by the imbalance in the three doshas. The predominance of a dosha in an individual's constitution indicates his or her vulnerability to a particular disease. Diseases in Ayurveda are classified according to thee origin of their causes.

Diseases which originate from factors within the human body, including psychosomatic diseases, are called adhyatmika. Adhyatmika diseases are further divided into hereditary diseases, congenital diseases and those caused by the aggravation of the doshas. Adhibhautika diseases are those whose origin can be traced to external physical factors such as germs and accidents. Adhidaiveka diseases are caused by the seasons, planetary influential, providential causes and so forth.

The physician diagnoses a disease in an individual by an examination of the patient based on three general methods. These methods are common to understanding any phenomenon in the universe.

Direct observation or pratyaksha: This is done through the senses: seeing, hearing, smelling, touching and tasting. A direct contact between the senses and the object of examination is thus established.

Inference or anumana: Just as one deduces that there is a fire when one sees smoke, one can make deductions in the observation of certain substances under the microscope. For instance, the examination of stool under a microscope will give clues about the state of the health of a person.

Authoritative statement or shabda: Experts have bequeathed to us a legacy of authoritative statements regarding diseases. The patient is interrogated closely to determine the exact nature of the diseases. The patient's relatives too are questioned for in this way the patient's previous history of diseases can be recorded. Fortified with the knowledge from previously recorded cases and the findings of experts, the physician can make a diagnosis.

Following these three principles, a brief examination of the patient proceeds in three stages: visual observation or darshana, touch or sparshana, interrogation or prashna. Another tool of diagnosis in Ayurveda involves the eight-fold method of examination or ashtasthana pariksha which has the following steps:

Applying these methods of examination, an experienced physician is able to comprehend a general impression about the patient's individual constitutionand which dosha or combination of doshas is affected. The treatment can thus be broadly identified.

The physician may ask the patient a few questions. For example, if the physician feels that a headache may be caused by a stomach problem he may ask the patient about the food he ate the previous night. Interrogation is thus also a tool of investigation and diagnosis. Ayurvedic classics caution the physician against being very specific in naming the disease in a patient . Names are attributed to some diseases purely in order to facilitate and aid the physician in ascertaining and understanding the entire gamut of the remaining diseases for which names are not furnished.

It is however essential to determinate the exact nature of a disease in order to prescribe the proper treatment. Each disease must be studied with regard to the following points:

	Causes of diseases or nidana.
	The premonitory signs or symptoms or purvarupa.
	The actual signs or symptoms or rupa.
	Exploratory therapy or upasaya.
	The mode of manifestation of the disease or samprapti.

Causes of disease may vary. Some factors may cause diseases to appear quite early; others may have delayed effects; yet others may not be strong enough to cause disease. There are also some which cause instantaneous effects, for example strong poisons. Various types of diets, regimens and the effects of the seasons are exogenous factors which cause disease. The endogenous ones are attributed to the doshas and tissue elements. Premonitory signs can be general or specific in indicating the nature of the disease that will manifest itself. They provide a clue to the diagnosis of the impending disease. At this stage some diet restrictions as well as administration of medicines may avert the onset of the actual disease. Exploratory therapy is carried out to arrive at the correct diagnosis of a disease of doubtful identity. Actual signs and symptoms of the disease become manifest if it is not averted during the premonitory stage. The signs and the symptoms of the disease are related to the site of its origin or udbhava sthana, the site of its manifestation or adhisthana and the path of transportation or sanchara marga. All actual signs and symptoms are also related to the doshas, tissues, enzymes and channels of circulation.