There is God. The only example—several times I have cited—that existence of God can be perceived with very simple... What is that? Just like you can perceive your existence in this body by the consciousness... You have got consciousness. That point we have discussed several times. That consciousness is the symptom of your existence in this body. So long that consciousness is there, this bodily function is going on very nicely.
Now, you are eating. You do not know how your foodstuff is going to the stomach, how it is being transformed into different kinds of secretion, how it is being transferred from the stomach to the heart, how that secretion becoming red, and that red blood is again circulated from the brain to the toe. These nice machinery work is going on within your body. This physiological condition is present in your body. You are taking your foodstuff. The necessary juice, vitamins, are taken by the stomach. It is distributed, and the exhaustion of your body is supplemented, and the unnecessary things evacuated by stool, urine. The nice thing is going on. Now, as soon as this consciousness is stopped, will this function go any more? No. You will find the same brain is there; the same heart is there; the same stomach is there by dissection of the body. You will see the same veins. Everything is there complete. But only thing is wanting—that consciousness. Therefore everything is stopped. This is a common factor. Everyone can know it.
Similarly, the whole cosmic manifestation which is present before you, so nicely going on, don't you think there is a consciousness behind it? How can you deny that there is no consciousness in the matter of sun rising, moon rising, seasonal changes, and so many planets floating in the air? So many wonderful things are being done in the material nature. Do you think it is without being done, consciousness? No. There is also consciousness. Just like for the management of your own body, due to the consciousness everything is being well done, similarly, everything that you see very nicely well done in the material nature, that is also being done by superior consciousness. This is human reasoning. How can you deny it? Can you deny it? I don't think any sane man can deny it.
Similarly, as your consciousness is a symptom of your presence, you are spirit soul, similarly, the supreme consciousness is the symptom of the supreme soul, or God, the supreme God. This is the position. Now, as consciousness, we are part and parcel of the supreme consciousness. Therefore, the whole business of our life is to dovetail our activities with the supreme plan. That is called karma-yoga. That is called karma-yoga. Eko bahu syāt.
In the Vedic literature you will find that God has expanded Himself into many, just like the father expands himself into many children. The children is nothing but expansions of the body of the father. Similarly, we, all living entities, spiritual parts or living souls, we are also expansion of the supreme spirit. Now, the reason is, why the supreme spirit soul expanded himself into so many? What is the purpose? We have to understand. Now you can take the example. What is the purpose of father's expanding himself into children? A father takes the responsibility of maintaining the children. Why? Why he takes such, I mean, a grave responsibility, a family man. That "why" is answered—just to have happy and enjoyable life. That's all.
Similarly, God has expanded into so many living entities because He wants enjoyment. He wants enjoyment. Because you will find in the Vedic literature that the nature of God is sac-cid-ānanda-vigraha (Bs. 5.1). Ānandamayo 'bhyāsāt: (Vedānta-sūtra 1.1.12)"By nature He is enjoying." So we must understand that God has expanded Himself into so many living entities just for His enjoyment. Now, we are meant for... Just like sons, children are meant for satisfying the father, similarly this is a common sense affair, that we living entities, we are meant for satisfying the Supreme. That satisfaction of the Supreme can be done by performance of yajña. That is the beginning.
So here it is prescribed that yajñārthāt karmaṇaḥ anyatra (BG 3.9). That is... We have discussed. Yajña-śiṣṭāśinaḥ santo mucyante sarva-kilbiṣaiḥ (BG 3.13). If we perform sacrifice for the satisfaction of the Supreme, then the result will be that we shall be free from all reaction of our sinful life. And if we do not do that, bhuñjate te tv aghaṁ pāpā ye pacanty ātma-kāraṇāt. Ātma-kāraṇāt means simply for his own sense gratification.