Nobody doubts that he exists, though he may doubt the existence of God. If he finds out the truth about himself and discovers his own source, this is all that is required.
Ramana MaharshiTill you reach the state of jnana and thus wake out of maya you must do social service by relieving suffering whenever you see it. But even then you must do it without ahankara, i.e., without the sense of 'I am the doer', but with the feeling 'I am the Lord's tool'.
Ramana Maharshi