Nidāna-sthāna, the second book of the Caraka Saṃhitā—an ancient Ayurvedic classic traditionally attributed to Ācārya Caraka and later redacted by Dridhabala—lays out the art of diagnosis. Rooted in centuries of clinical observation, it systematically explores nidāna (causes), samprapti (pathogenesis), lakṣaṇa (symptoms), disease stages and prognosis, plus epidemic and psychosomatic influences. Key themes are multifactorial causation, doshic imbalance, individualized clinical signs, and the imperative of early detection and nidāna-parivarjana (avoidance). Its epidemiological insights, emphasis on lifestyle and environment, and holistic diagnostic framework remain highly relevant—informing preventive medicine, patient-centered assessment, and integrative approaches in today’s healthcare.