Man will then look for something ABOVE HIMSELF worthy to worship and believe in. This is the amazing spiritual nature of man, which makes him unique and also makes him accountable. It is the inner discussion he has with his own SOUL, which distinguishes the human being from the ANIMALS.
If he is guided, he will find the One True God, and will fulfil his need to worship by believing in Him and obeying the Divine Inspiration sent by Him. This is basically the meaning of Islam; surrender to the Lord and Sustainer of the Universe - Allah.