Westminster Larger Catechism (Q2)

Q. 2. How doth it appear that there is a God?
A. The very light of nature in man, and the works of God, declare plainly that there is a God; but his word and Spirit only do sufficiently and effectually reveal him unto men for their salvation.

What does this mean?
Simply put: God reveals himself through nature and also through the awareness of man.  It is obvious and evident that He exists, but He does not reveal Himself fully through these avenues. It is only through the written word and the actions of the Spirit that God is revealed in a saving way.  In other words, a person may realize that there is a God, but apart from the Word of God and the quickening of the Spirit, that revelation will never be personal and will never lead to true spiritual regeneration (salvation).

What does this mean for me?
 There are great personal implications in this Q and A of the catechism.  The first is inward, if not for the work of the Spirit, I would not be saved.  If not for the Word of God, there would be no salvation.  Therefore, there should be a deep gratitude to God for His revealing word in the scripture and through the Spirit for my own Salvation.

Also, outwardly, this should drive us to spread the Word.  As it says in Romans 10:14-15 -

How then will they call on him in whom they have not believed? And how are they to believe in him of whom they have never heard? And how are they to hear without someone preaching? And how are they to preach unless they are sent? As it is written, “How beautiful are the feet of those who preach the good news!”

We must go and preach the word, without it and without the moving of the Spirit, none will come to salvation.