In order to understand  the ayurvedic aproach to herbs, one must understand the basic system of Ayurveda, which is a complete healing science, including the physical

psychological and spiritual aspects of life. The ancient seers of India envisioned two fundamental principles behind existence: Purusha, the Primal spirit, the principle of

sentience of  consciousness; and the Prakruti, or Great Nature, the principle creativity. The union of these two, Spirit and matter produce all things.

Yet these two are also one, the primordial Two-in-One, consciousness and its executive force, Shiva-Shakti. Within all things is essence, individuality, consciousness-the

Purusha. Within all things is also the power of manifestation, the capacity for creative enfoldment-Prakruti. From these two great forces in their initial coming together is

born Cosmic intelligence, Mahat,which contains the seeds of all manifstation. Inherent in Mahat are all the laws of nature.

The cosmic intelligence also exists in the human being as the intelligence in the individual. As such it is called Buddhi, the meaning of awakening, developing fully when one becomes enlightened a Buddha.  Buddhi is our capacity for perception, our ability to disern the real from the unreal.  But this intelligence, in its evolution into material forms, may give rise to the ego, the sense of seperate self, or Ahamkar. It is the principle of  division as it is only our sense of a seperate ego that divides us from the unity of life.

In turn, the ego gives rise to the conditioned mind or conditioned consciousness called Manas, which, as our sense of self-consciousness, creates a protective thought-field around itself in which we become bound. Finally, this links us upwith the collective unconscious called Chitta, the storehouse of thoughts of all limited mentalities. Through Chitta we remain under the influence of the latencies, compulsions and drives of the earlier  stages of evolution, going all the way back to the animal realm and before.

Ayurveda aims at a life in harmony  with Cosmic  Intelligence, whereby our own intelligence is perfected, so that through it we can return to unity with nature to our true

self and spirit, the Purusha. This is the spiritual background of Ayurveda,which is the same  as that of yoga,  and the basis of Ayurvedic psychology.  This requires the

awakening  of intelligence wherein we go beyond  the rule of the ego. The ego  is the basis for all deviation from  nature. Health is natural, Prakruti. Disease  is artifical,

Vikruti. Hence, most diseases, except those natural to the course of time, are from the psychologlical  imbalance born of unnecessary self-consciousness.

Ref:The Yoga Of Herbs/Dr.David Frawley-Dr.Vasant Lad