Romans 1:19-20

Romans 1:19-20 For what can be known about God is plain to them, because God has shown it to them.  For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse.

In these two verses Paul explains natural revelation.  Mankind was made in the image of God and has the power to think and reason.  From this God given ability to think and reason it is evident that the creation that man sees and experiences has come about from only two possibilities.  One possibility is that a supreme being of immense power created the earth and everything in it.  The other possibility is that something came from nothing without an outside cause and not only that but it produced life, balance, and order.  Although the second option is pure nonsense, many secular humanists and even eminent scientists are endorsing this option.  This is a great example of suppressing the truth that Paul described in the prior verse.  Therefore, even people who have never heard about the written revelation of God are without excuse.  Also, Paul goes on to explain in chapter two that the works of the law are written on people’s hearts. 
 
From this point through Romans 3:20 Paul explains the bad news concerning man’s sin and his hopeless predicament in and of himself with his creator.