"If you know that He is righteous, you know that everyone also who practices righteousness is born of Him."

Jesus told us the same thing:  Do not say that I am good, only the Father is good...

The truth is in nature and all around us.  Good gives birth to good.  Apples give birth to apples.  Joy gives birth to joy...  Righteousness gives birth to righteousness.

This is how, according to John, you can tell that you are walking with God, walking in the light.  If you do the works of the Father.

In other words, John asks us to take a look at ourselves and discover how closely connected we are to the Savior.

If you seek righteousness - seek the source of righteousness.