The effectivity of the word of God in a person's life does not
depend on the eloquent words of the preacher. Every man is endowed by
God with intellect and will to choose the things he or she believes in.
The fulfillment of the Lord's promises in the bible relies on the
person's willingness to accept these promises.
Imagine
a mailman approaching your front door carrying a huge package. You
receive the package and ask the man where it came from. You are
surprised to be receiving such a big package. You begin to wonder what's
inside it. For as long as the mail man is concerned, he can only tell
you the name and location of the origin of that package. What's inside
that package? Who is that person giving you that package? And why is
that person giving you that package? The mail man could not give you the
exact answers to all those questions. But you would
already get an idea why the person had sent you that package once you
discover his name and identity. Most likely, you have a certain
relationship with the person sending you the package, i.e. parents,
intimate friends, lovers. So you will no longer question the intention
of the person sending the package and move on to enjoying the gift that
you have received.

The word of God is like a Christmas
present. The priests, missionaries, pastors, evangelists and even your
Christian friends are simply acting as the mail man. They are only
carrying the word of God as a package to be delivered to you. You can
ask all the logical questions about the word of God from other people
but you will never find it's true significance in your life based on
their answers. You will need to look into your relationship with God to
understand the true meaning of His gifts.