Bhagavad Gita: Chapter 15, Verse 10

उत्क्रामन्तं स्थितं वापि भुञ्जानं वा गुणान्वितम् |
विमूढा नानुपश्यन्ति पश्यन्ति ज्ञानचक्षुष: || 10||

utkrāmantaṁ sthitaṁ vāpi bhuñjānaṁ vā guṇānvitam
vimūḍhā nānupaśhyanti paśhyanti jñāna-chakṣhuṣhaḥ

utkrāmantamdeparting; sthitamresiding; vā apior even; bhuñjānamenjoys; or; guṇa-anvitamunder the spell of the modes of material nature; vimūḍhāḥthe ignorant; nanot; anupaśhyantipercieve; paśhyantibehold; jñāna-chakṣhuṣhaḥthose who possess the eyes of knowledge


BG 15.10: The ignorant do not perceive the soul as it resides in the body, and as it enjoys sense objects; nor do they perceive it when it departs. But those who possess the eyes of knowledge can behold it.


Although the soul is seated within the body and savors the perceptions of the mind and senses, not everyone cognizes this.  The reason is that the soul is non-material and cannot be seen or touched by the material senses.  Scientists cannot detect it in laboratories with their instruments, so they mistakenly conclude that the body is the self.  This is like a mechanic trying to figure out how a car moves.  He traces the movement of the wheels backward and reaches the accelerator, the ignition switch and the steering wheel.  He labels these as the car’s causes of motion, without realizing that it is a driver who operates these.  Similarly, without knowledge of the existence of the soul, physiologists conclude that the bodily parts together are the source of life within the body.  

However, those who have walked the path of spirituality see with eyes of knowledge that the soul energizes these bodily parts.  When it departs, even though all the different organs of the material body such as the heart, brain, lungs, etc. are all there, consciousness ceases to exist.  Consciousness is a symptom of the soul; it is present in the body as long as the soul is present and leaves when the soul leaves.  Only those who possess the eyes of knowledge (jñāna chakṣhu) can see this.  Shree Krishna says here that the ignorant (vimūḍh), unaware of their own divine identity, presume the corporeal body to be the self.