CHAPTER 18 · VERSE 32
Bhagavad Gita 18.32
अधर्मं धर्ममिति या मन्यते तमसावृता। सर्वार्थान्विपरीतांश्च बुद्धिः सा पार्थ तामसी॥
That intellect which, enveloped in darkness, regards unrighteousness as righteousness and sees all things upside down, is Tamasic, O Partha.
Tamasic intellect is completely inverted: mistaking evil for good and harm for virtue.