Bhagavad Gita Verse 18.22

परन्तु जो ज्ञान एक कार्य रूप शरीर में ही सम्पूर्ण के सदृश आसक्त्त है तथा जो बिना युक्त्ति वाला, तात्विक अर्थ से रहित और तुच्छ है —- वह तामस कहा गया है |

However dear Arjuna, if one selfishly views one particular thing (namely the body) as if it is all and everything that is to be concerned about, the knowledge he possesses does not allow him to see beyond the perishable objects and beings in this world. He considers himself the one and only, independent, and seperate from all other beings in this world.