However, I believe God still speaks in the here and now. Why?
(1) Some people say they just believe in the Bible. But what is the Bible? It's a collection of books written by people inspired by God, about people who interacted with God.
(2) I've heard/felt/sensed God speaking to me too.
My other reasons are taken from the Bible we* both place our faith in.
(3) Jesus promised the Counselor, the Holy Spirit.
"All this I have spoken while still with you.
But the Counselor, the Holy Spirit, whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you." (John 14:25-26)
(4) There will be more --- not less --- of the Holy Spirit in the last days!
"In the last days, God says, I will pour out my Spirit on all people.
Your sons and daughters will prophesy, your young men will see visions, your old men will dream dreams.
Even on my servants, both men and women, I will pour out my Spirit in those days, and they will prophesy.
I will show wonders in the heaven above and signs on the earth below, blood and fire and billows of smoke.
The sun will be turned to darkness and the moon to blood before the coming of the great and glorious day of the Lord.
And everyone who calls on the name of the Lord will be saved."
(Joel 2:28-32, recounted in Acts 2:17-21 as it starts to be fulfilled)
(5) The promise of the Holy Spirit is available even to us.
Peter replied, "Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins.
And you will receive the gift of the Holy Spirit.
The promise is for you and your children and for all who are far off—for all whom the Lord our God will call." (Acts 2:38-39)
(6) Reading only the Bible because "God's word is complete" is similar to not working on the Sabbath because "God's work is complete." But how did Jesus respond?
So, because Jesus was doing these things on the Sabbath, the Jews persecuted him.
Jesus said to them, "My Father is always at his work to this very day, and I, too, am working." (John 5:16-17)
(7) The last verse of the Gospels admitted that the Bible and the whole world could not contain all that Jesus did. How much more now, two thousand years later?
Jesus did many other things as well.
If every one of them were written down, I suppose that even the whole world would not have room for the books that would be written. (John 21:25)
(8) Yes, all Scripture is useful. Mark* quoted 2 Timothy 3:16-17, but nowhere there nor elsewhere in Scripture does it say that it's all we need. If we hear something now, is it our own wishful thinking, or demons deceiving us? We can check the Bible if what we hear is in line with God's character, His message and His purposes. We can also check to see if God does speak in the first place.
All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work. (2 Timothy 3:16-17)
(9) We need not worry too much if we're not sure about God's voice. If He really wants to tell us something (and if we really want to follow), He'll make a way.
My sheep listen to my voice; I know them, and they follow me.
When he has brought out all his own, he goes on ahead of them, and his sheep follow him because they know his voice. (John 10:27,4)
(10) Those who follow Jesus would do well to remember what He said was the only unforgivable sin:
And so I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven. Anyone who speaks a word against the Son of Man will be forgiven, but anyone who speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come. (Matthew 12:31-32)
Postscript: Thanks to "Waking the Dead" by John Eldredge
"I have much more to say to you, more than you can now bear. But when he, the Spirit of truth, comes, he will guide you into all truth. He will not speak on his own; he will speak only what he hears, and he will tell you what is yet to come. He will bring glory to me by taking from what is mine and making it known to you. All that belongs to the Father is mine. That is why I said the Spirit will take from what is mine and make it known to you. (John 16:12-15)
* Originally posted as a comment on http://three17.blogspot.com/2005/10/hope-does-not-disappoint-part-2-2.html