Our mind is material, so it can't imagine anything Divine. So, the form we create in our mind is a material form. However, if we have faith that Krishna is in this form I've created, now you've attached your mind to Shri Krishna. So, although your imagination is a material thing, but real Divine Shri Krishna is in that imagined image. So, you get a Divine result. Even though we're incapable of visualizing His actual form, we still get a Divine result from our material effort because of His grace. He's omnipresent, so He's in our imagined form as well. We just have to have that bhagwad bhavana (God feeling).
Same thing if we worship a murti. The bhagwad bhavana has to be there.
शैली दारुमयी लौही लेप्या लेख्या च सैकती । मनोमयी मणिमयी प्रतिमाष्टविधा स्मृता ॥
Shailī dāru-mayī lauhī lepyā lekhyā cha saikatī. Mano-mayī maṇi-mayī pratimāṣhṭa-vidhā smṛitā.- Srimad Bhagwatam 11.27.12
The Bhagwatam says there are eight main ways to make a murti, a deity of God, an image of God.
You can make one shaili, means carved out of stone. So, if you worship a shaili murti with bhagwad bhavana, you'll get God realized.
Or darumai: you can make it out of wood.
Or lauhi: out of metal, any combination of metals.
Lepya: out of clay.
Lekhya: something an artist creates, a drawing, a painting.
Saikati: out of sand.
Manimai: out of a jewel or jewels.
And finally, manomai: you created it in your mind, which is what Shree Maharaj Ji recommends for us to do.
He says, “Leave the other murtis. You don't want to be bound by the do's and don'ts of taking care of a murti properly.” So, just make your murti in your mind and infuse your meditation with bhagwad bhavana and now you'll get the correct result.
Just like Shri Krishna pervades the murti, the stone murti, He pervades the manomai murti in your mind. When Shukdev Ji was explaining to King Parikshit the Aghasur leela, that demon who came and took the form of a huge python and swallowed up all the gwalbals (cowherds and friends), Shri Krishna came, entered into his mouth and killed him and revived all of His friends. And of course, once he had been killed, he was actually released from that demon form that he had been born as, and he entered into Shri Krishna, entered into His Divine abode.
So Shukdev Ji said, “Such is the amazing grace of Shri Krishna.” He said, “Parikshit, you shouldn't be amazed that Aghasur got delivered by Shri Krishna.” I mean, Shri Krishna entered right into inside his body and with Krishna's Divine touch Aghasur became surrendered and he went to the Divine abode. So, what to say of Aghasur having God come and enter his own body. Even if a person just imagines the form of Shri Krishna and attaches their mind faithfully to that form, even that person goes to the Divine abode.
So, this is the effectiveness of roopdhyan.
