यत्तु कृत्स्नवदेकस्मिन्कार्ये सक्तमहैतुकम् | अतत्त्वार्थवदल्पं च तत्तामसमुदाहृतम् ||
yat tu kṛtsnavad ekasmin kārye saktam ahaitukam atattvārthavad alpaṁ ca tat tāmasam udāhṛtam
Translation
But that which is attached to one single effect as if it were everything, without rational basis, and without grasp of the truth — that is declared tamasic.
Interpretation
Tamasic knowledge: fixation on one limited thing as if it were the whole, without any rational grounding, and without access to reality. This is knowledge that is 'narrow, irrational, and unreal' — dogmatic attachment to a partial view that mistakes itself for the whole truth. The tamasic knower cannot see beyond their fixed idea, their prejudice, their superstition, their ideology. They hold their limited knowledge with absolute conviction. This is the most dangerous kind of ignorance: certain of being right, but completely wrong.