Cause and effect are mediated across time. Every activity of mankind happens with reference to Kāla. The fundamental principle of Kāla, apropos the present idea of time, gives an insight into the profundity of Āyurvedicic literature. The Ācāryas of Āyurveda, namely, Caraka and Sussruta gave very reflective definitions of Kāla. These ideas reverberate with the contemporary notion of time.
Two types of Dravyas (matter) have been described in the Āyurvedic texts, i.e. Kāraṇa Dravya (causal matter) and Kārya Dravya (effectual matter). Kārya is Vyaktāvasthā (manifested stage) and Kāraṇa is Avyaktāvasthā (unmanifested stage). It is only the transformation of form or stages (1).
Kāraṇa (causal) — there are nine Kāraṇa Dravyas, which constitute the building-blocks for all the transformation in the universe. They are Pañca Tanmātrās (subtle forms of five elements) — Ākaśa (Ether), Vāyu (Air), Agni (Fire), Jala (Water) Pṛthvī (Earth) with Mana (Mind), Ātmā (Consciousness), Kāla (time) (2) and Diśa (space).
Kārya (effectual) — all the visible and invisible matter of the universe constituted from Kāraṇa Dravyas are Kārya Dravyas. These are innumerable.
Kāla was characterised by Maharṣi Suśruta as Swayambhu (it originated itself), Anādi-madhyanidhanaḥ (it is without beginning, peak and end). It is mobile in the Sūkṣmatama Kalās (does not stop in the subtlest fractions) (3).
According to Ācarya Caraka, Kāla is the process of Pariṇāma (transformation) (4). Since Āyurveda is a science of life, the division of Kāla is important. It finds application in various ways pertaining to wellness and illness.
On a broader scale, Kāla can be divided as:
Nityag Kāla (general scale of time as day-night, seasons, etc.) and in a definite wedge as the stages of disease called Avasthika Kāla (5).
