Introduction

For a long time, health was understood through the idea of bodily 'humors' being in balance — a view held by early Greek physicians like Hippocrates and by the Indian Ayurvedic tradition alike. Under this framework, a person with excess 'black bile' was thought to have a 'hot' personality prone to fevers — a conclusion reached through pure reasoning, not experiment. That view didn't survive contact with actual evidence: William Harvey's experimental discovery of blood circulation, and the simple demonstration that people with supposedly excess 'black bile' didn't actually run hotter when measured with a thermometer, disproved the humors theory. Modern biology instead recognises that the mind influences the immune system through the nervous and endocrine systems — so mental state genuinely affects physical health. Beyond that connection, health is shaped by three broad factors: genetic disorders (deficiencies present from birth or inherited from parents), infections, and lifestyle (diet, water, rest, exercise, and habits).