The meaning of God is just too wide for simple definitions. How can man place define something that is incomprehensible to us, as small particles in huge universe. We first need to pay attention to all that we as humans have learned. If "God" is the creation of man let us look at what man knows to have a clear vantage point of my point and an understanding of why the Source cannot logically be a creation of the mind.
We know that every piece of matter is organized in similar patterns, atoms, DNA and galaxies have what in common? Take a look at a picture and tell me the same patterns that exist in the smallest parts of matter on earth are made in such similarity to the solar system, the galaxies and now the clusters of galaxies. We know that we are complex creatures who have now been able to understand the deep workings of our mind and bodies. We have scientific studies that prove patients who are prayed for heal at a faster rate than those who are not. Patterns of brain waves prove the electrical difference in brain waves of loving and gentle thoughts versus hateful and angry ones. We have diffused matter into tiny pieces and still don't understand how all things are only electric currents at various speeds. From the elements in the periodic table to the beats of our hearts and the radio waves we listen to are from that energy.
The basic beliefs of modern man aren't too much different from the thoughts of primitive man when you think about it. Prehistoric man had a terrible hurricane he blamed the Gods, they had angered them, they became fearful. Modern man with knowledge of storm systems, understanding of weather patters and can see a storm coming on radar can still say the same things. "It is the judgment of God on those people, we have sinned, an act of God". Whether earthquakes, terrorism, weather related catastrophe, who gets the blame? God! How interesting that modern man who feels so superior to his ancestors has the same reactions to things not understood.
As man has viewed life on the third rock from the sun, he has seen life and death. All things here on earth are born, live and die. All things except the cycles of nature on which our survival depends. Each year from summer to fall, winter to spring and all is reborn. Our moon, grows beautiful and full then disappears to a black spot in the sky every 28 days, a womans menstrual cycle where life springs from is on 28 day cycle. These are the things that ancients took into account when they formed their understanding of God. Today we have ignored the reproductive nature of the planet, drained the resources and the results are only now becoming clear. We would do well to pay attention to the rhythm of the planet.
Factoring in general ideas from science, a bit of common sense and the patterns and nature of man you will see that God is not a product of the mind. In all history man has looked to something greater than himself, from the cave to the International Space Laboratory we ask ourselves the same questions. If indeed a creation of the mind then why hasn't the basic understanding of God changed in all these many millenniums? There has been no maturation of the concept, gods today have the same petty qualities as the gods of mythology, though not expressed so obviously. The deep understanding of the Eastern mystics has remained constant and the wisdom of those of old is still valued. Why have similar concepts persisted all this time, so many of the billions of souls that have lived on the earth had a belief in something greater than themselves.
The Source, the spark from which all energy sources for all the matter in the Universe sprang, that is God. All the specifics are merely the way man has understood the Creator, which is this Source man believes is able to be reached. All men have sought God and always will. It is something buried deep inside man, a knowing there is something more. We are connected to something greater than ourselves and many claim to have a relationship with it. Whether you define it as the Universe, God, Allah, Venus, Apollo, Jehovah, Source, Jesus, a living force, or whatever way you perceive it, you cannot deny the evidence. God of some sort exists, whether merely the power that holds the universe together devoid of personality if you choose, or a personal entity who is involved in our daily lives as I do.