In our conditioned state, we cannot know about the spiritual world. But the spiritual world exists. As Lord Krsna states in the Bhagavad-gita (8.20), paras tasmat tu bhavo nyo: Besides this inferior, material nature there is another, superior nature. This material nature is one nature, comprised of millions and trillions of universes clustered together in one corner of the spiritual sky. We cannot even measure the sky covered by this one universe, within which there are innumerable planets; yet there are millions and trillions of universes in the entire material creation. And the entire material creation is only one fourth of existence. In other words, this whole material world is existing in one fourth of Krsnas energy. The other three fourths comprise the spiritual sky. Unfortunate persons think that this planet is all in all, but this is frog philosophy. A frog in a well cannot understand anything beyond the well, and he measures everything in terms of his well. When he is told about the ocean, he cannot imagine it. Similarly, persons with such a frogs mentality imagine, God is like this, or Gods kingdom is like that, or I am God, or There is no God. But this is all foolishness.