(i) Aptopadesa (Authoritative Testimony): One who is free of doubts, enmity, fear, arrogance, indignity, self-importance, ignorance and who has gained certainty, complete and practical knowledge of his subject, one who is able to express the subject knowledge for the well-being of humans, such persons are called ‘apta’ or ‘sista’ (authorized or reliable). Caraka says “those who are free from ‘rajas’ and ‘tamas’ (‘rajas’ is the root cause of attachment and aversion, while ‘tamas’ is the covering of ignorance; these defects make a person unfit for being in a position of authority) and endowed with strength of penance and knowledge; whose knowledge is without defect, always uncontradicted are known as ‘apta’ (having acquired the knowledge) or ‘sista’ (expert in the discipline).” They are free from ambiguity or doubt, which is true as they are devoid of ‘rajas’ and ‘tamas.’ ‘Sista’ means ‘with knowledge of the scriptures’ as well as ‘of noble conduct.’ Thus ‘apta’ or ‘sista’ are credible persons, devoid of doubts, acquisition, attachment and aversion. The discourse, sermon or scriptual testimony of such learned persons is termed ‘aptopdesa’ or ‘sabda pramana’ (authoritative statement of those having acquired perfect knowledge). Usually, knowledge obtained by such a person in each subject is the first step in examining a disease, followed by direct observation and inference, which further verifies a disease.
According to Ayurveda, a physician who has not gathered knowledge about diseases by aptopdesa can not determine a disease by observation and inference.
Caraka Samhita, Susruta Samhita, Astanga Hrdaya and other treatises are the scriptual testimony (aptopadesa) in Ayurveda. By means of these, a practitioner can gather knowledge regarding a specific disease, its causes or diagnosis, imbalance of dosas and vitiated tissues, the form and type of a disease (whether physical, mental, internal cause, external injury and others), location of a disease, the spreading path of a disease, preliminary signs, symptoms, diagnostic symptoms, category of a disease; whether curable, incurable or which can relapse, complications of a disease, name of the disease, type of treatment required, and compatible and incompatible diet for a patient. An appropriate knowledge of these facts and other such types of useful information are not possible without aptopadesa. Hence, aptopadesa is an important method to assay a disease.
(ii) Pratyaksa (Perception or Direct Observation): Perception is the knowledge acquired by interaction of the sensory organs (eyes, ears and so on) with their subjects. The clear knowledge (indisputable and complete) that arises by mutual association of self (soul), mind, sensory organs and their subjects is termed as pratyaksa (perception or observation). In brief, the information obtained by self-recognition with the help of the subjects by the sensory organs and its perception by the mind is termed as ‘pratyaksa.’
This definitive information in the form of perception is obtained by mutual connection with the soul, and essentially requires a definite sequential order. This involves, the connection established between the soul and mind, mind to sensory organs and sensory organs with their concerned subjects through the stimuli received from the external environment.
With the help of observation and perception, except for the tongue, the remaining sense organs (eyes, ears, nose and skin) and their concerned actions (visualization, hearing, smell and touch) are essential for examining a disease. A disease is diagnosed by visualizing the color of the skin of a patient; shape, measurements and constitution of the body; brightness and glow in the body and eyes; natural or abnormal expression of the body; color of the wound; inflammation and its types; substances eliminated in the stool, urine, phlegm, blood and vomit; menstrual blood, pus discharge from wounds and so on. For the assay of disease, auditory perceptions help to analyze the gurgling sound produced by the stomach and intestines; the cracking sound produced by the flexion of knee and finger joints; heartbeats and sound perception from lungs and other organs; and the voice of a patient. Olfactory perceptions help to detect the patient’s body smell and smell in the feces, urine, phlegm, blood, sweat and wounds for disease examination. Fever, edema, body temperature and heat generated on the surface of the abscess or wounds, coolness, softness, hardness, roughness, smoothness, dryness, pulse and other perceptions can be examined by touch. All these sensory analyses are included in the knowledge of perception or observation (pratyaksa).
In modern days, different types of equipments and techniques are available for the assay of disease like the stethoscope for heartbeats, the thermometer for temperature and the sphygmomanometer for blood pressure. In modern medical science, whichever technique being used for the diagnosis of a disease, be it different blood examinations, ultrasound, X-rays, CT Scan, MRI, angiography and endoscopy, comes under direct observation or perception establishing the cause of a disease.
(iii) Anumana (Hypothesis or Inference): The word ‘anumana’ is derived from two words ‘anu’ + ‘mana.’ To derive an actual fact about related incidence by visualizing its signs is ‘anumana’ (hypothesis or inference). Inference is the knowledge of a signee (disease) on prior perception of the sign. At first the sign is perceived, thereafter the knowledge of the signee (disease) arises with the application of invariable concommitance. Just as one on seeing smoke infers about a hidden fire and establish a confirmation, similarly smoke rising far in the sky helps to infer about a fire somewhere near. A conclusion based on facts is ‘anumana.’ According to Charak, ‘anumana’ is the fact that expects experimental confirmation. In simple words, ‘anumana’ is to know the unknown subject or event consequent upon the union of two or more causative factors on the basis of experimental confirmation.
It is not possible to examine many diseases and their symptoms by the valid knowledge of perception. Therefore, to examine these diseases, inference or hypothesis is required. Examination of taste (rasa) of a patient cannot be obtained by the knowledge of perception; hence, it can only be examined by inference. For example, on the basis of digestion and metabolism of food, one can analyse the strength and work done by the digestive fire in a patient’s body, and exercise helps to analyse the body strength and efficacy of a patient.
Knowledge of auto-immune diseases can be gathered only through hypothesis or inference. Sometimes it is difficult to identify a disease by direct observation or by authoritative or scriptual testimony and the fact that the patient is suffering from a difficult situation. At such time, a hypothesis or inference is helpful to identify the disease.
(iv) Yukti (Reason): ‘Yukti’ means intellect or reason or understanding of an object. It is an experimental confirmation. It is defined as the knowledge of intellectual perceptions or understanding of an object or event which sees the things produced as a consequence of a combination of multiple causative factors, valid in the three known time phases (the past, present and future) and is also helpful to achieve the three objects or goals of life (virtue, wealth and lust) is known as ‘yukti’ (reasoning). Just as the growth of crops depends on the combination of several factors such as water, ploughing, seed and season, so is yukti (reason) a rational and fruitful combination of all constituent factors. These four means of pramana (gain in knowledge), based on yukti (reasoning) helps to alleviate diseases if combined and used rationally. The essential factor in the successful treatment of a disease is ‘yukti’ (reasoning).