Bhagavad Gita · Chapter 18: Freedom through Renunciation
Bhagavad Gita 18.22
यत्तु कृत्स्नवदेकस्मिन्कार्ये सक्तमहैतुकम् ।
अतत्त्वार्थवदल्पं च तत्तामसमुदाहृतम् ॥
yattu kṛtsnavadekasminkārye saktamahaitukam | atattvārthavadalpaṃ ca tattāmasamudāhṛtam ||
And the knowledge that clings to one single thing as if it were the whole, without reason, without any grasp of the truth, and narrow, is said to be of inertia.
Modern context
Tamasic knowledge clings to one small thing as if it were everything, without reason or real understanding. This is the narrow, rigid view of a fanatic or of a person obsessed with one thing. It mistakes a fragment for the whole. Much harm comes from people who have fixed on one idea and will not see anything beyond it.