It would not be an exaggeration if I said that doubt is a disease, a disease which takes away faith. It would be more appropriate to say that doubt is the rust that eats the iron-like faith. It is very easy to allow doubts to work, and it is difficult to keep faith. However much a person may be evolved, there comes a time when doubts take hold of him. And the moments when the person is in doubt the light of intelligence disappears.