KATHOPNISHAD CHAPTER 5 SHLOK 9

                                                         अग्निर्यथैकोभुवनं प्रविष्टो 

                                                        रूपं रूपं प्रतिरूपोबभूव ।

                                                        एकस्तथा सर्वभूतान्तरात्मा

                                                     रूपं रूपं प्रतिरूपोबहिश्च ॥ ९

                                        AGNIR  YATHA  EKO BHUVANAM  PRAVISHTO

                                              RUPAM  RUPAM  PRATIRUPO  BABHUV |

                                          EKASTTATHA  SARVBHUTAN  ANTARATMA

                                          RUPAM  RUPAM  PRIATIRUPO BAHISCHA  ||9

AS THE FIRE WHEN IT ENTERS THE WORLD HAS DIFFERENT FORMS DEPENDING UPON

 WHAT IT BURNS, SO DOES THE ETERNAL ATMANOF ALL LIVING BEINGS TAKES THE

 FORM ACCORDING TO THE FORM IT ENTERS, AND IT IS OUTSIDE THE FORMS ALSO  ||9

      This Shloka is similar to others and tells us same message in first half. that the Atman in all the living things is same . So the Atman in dog or cat or human beings is same  and we don't have different Atman for different living beings. The dog and cat and human beings all have the same Atman. The example given here is that of Fire. The fire in old days was used to cook food and have light in house and generate heat when we had cold temperatures. So the same fire did look different . The modern day we can look at electricity. The fan that works with electricity or the light bulb that gives us light with same electricity  and the cooking range that helps us cook food and so on. The electricity is the same but it looks different if you look at what theses DORMS or RUPA that it comes through. The electricity does not do anything as a function- fan -cooking range or night production. It does not care about the function. So it is independent observer , but washout the electricity none of these things could function without the electricity . The electricity does and can  exist outside of fan - cooking range or bulb.

    So the ATMAN is similar. ( There are some differences but they are not mentioned here ) The Atman helps mind intellect and physical body to function and without the Atman none of these things will work - look at dead body. The Atman is same but with different physical body and astral or subtle body it appears to be different . This is same as electricity and the instruments that it powers and make them function. The Atman or universal consciousness does pervade EVERYTHING  and when it enters or gets confined to one unit of physical body with subtle body , it acts as that individual and appears different. So the Atman is inside and outside too.