Freud the pioneer psychologist wrote a book on religion entitled "The Future of an Illusion".  Belief in God, he said, is the product of our needs.  As children depend on their father, so adults need a big Father figure in the sky.  Conclusion: Belief is psychological.  Turn the tables by pointing out that this argument rebounds.  Unbelief also is psychological.  Rejection of God is due to rejection or rebellion against parents.  Refusal to believe is usually not on rational grounds.  Aldous Huxley, a prominent atheist, wrote: "I had motives for not wanting the world to have a meaning; and consequently assumed that it had none, and was able without any difficulty to find satisfying reasons for this assumption.. . . For myself, the philosophy of meaninglessness was essentially an instrument of liberation, sexual and political." (Ends and Means, p. 270).  The unbeliever likes to think that he is more rational or scientific than the believer.  He is not.  Often he is not so much an unbeliever as a won't-believer.  "Now let us look at the solid facts and evidence of Jesus Christ."