अधर्मं धर्ममिति या मन्यते तमसावृता ।सर्वार्थान्विपरीतांश्च बुद्धिः सा पार्थ तामसी ॥
adharmaṃ dharmamiti yā manyate tamasāvṛtāsarvārthānviparītāṃśca buddhiḥ sā pārtha tāmasī
That which, enveloped in darkness, takes what is not the true law and upholds it as the law and sees all things in a cloud of misconceptions, that understanding , O Partha, is tamasic.
Gītā 18·32The tamasic reason is a false, ignorant and darkened instrument which chains us to see all things in a dull and wrong light, a cloud of misconceptions, a stupid ignoring of the values of things and people. This reason calls light darkness and darkness light, takes what is not the true law and upholds it as the law, persists in the thing which ought not to be done and holds it up to us as the one right thing to be done. Its ignorance is invincible and its persistence of will is a persistence in the satisfaction and dull pride of its ignorance. That is on its side of blind action; but it is pursued also by a heavy stress of inertia and impotence, a persistence in dullness and sleep, an aversion to mental change and progress, a dwelling on the fears and pains and depressions of mind which deter us in our path or keep us to base, weak and cowardly ways.