Belief is natural, and disbelief is unnatural, for belief is born in man, and unbelief is acquired. … Every child born on earth is born with a tendency to believe what is told him, but the experience of the individual in this world full of falsehood teaches man to disbelieve. That shows that every soul comes from the world of truth, and opens his eyes in the world of falsehood. Every child comes into the world with that purity of heart whose natural tendency is to believe and later he acquires the tendency to doubt. The Prophet has therefore said: ‘Every child is born a believer, it is afterwards that he becomes an unbeliever.’ … For doubt is earth-born and belief is heaven-born.

~~~ “Religious Gatheka 42, Belief and Disbelief in God”, by Hazrat Inayat Khan (unpublished)