Tamas is the Indian word for the principle of inertia of consciousness and force: a consciousness dull and sluggish and incompetent in its play is said to be tamasic; a force, a Life-energy that is indolent and limited in its capacity, bound to a narrow range of instinctive impulses, not developing, not seeking
farther, not urged to a greater kinetic action or a more luminously conscious action, would be assigned to the same category.

Tamas brings into our emotional nature insensibility, indifference, want of sympathy and openness, the shut soul, the callous heart, the soon spent affection and languor of the feelings, into our aesthetic and sensational
nature the dull aesthesis, the limited range of response, the insensibility to beauty, all that makes in man the coarse, heavy and vulgar spirit.

Inertia comes usually from the ordinary physical consciousness, especially when the vital is actively not supporting the sadhana. These things can only be cured by a persistent bringing down of the higher spiritual consciousness into all the parts of the being.

Heaven's call is rare, rarer the heart that heeds;
The doors of light are sealed to common mind,
And earth's needs nail to earth the human mass,
Only in an uplifting hour of stress
Men answer to the touch of greater things.