The religion of the ancient Hebrews (and thus of the Hebrew Bible) was based upon the belief that God can and does speak to man. ... The belief that God speaks to man is fundamental; we cannot accept some of the Hebrew beliefs as valid for modern man and abandon the basis upon which they are proposed, for this leaves them precisely baseless, unfounded (The Two-Edged Sword, McKenzie).
As moderns, we tend to be sceptical about God speaking to us. We may not doubt that he speaks to the great saints ("Francis, rebuild My Church!" for example), but most of us are extremely doubtful that He can or will speak to us. And yet, Jesus is very emphatic at the Last Supper about the role of the Holy Spirit in our lives: 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 (Jn. 14).
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 (Jn. 16).
Many of us have had the experience of "hearing" an inner voice directing us, and yet we have shut it down, thinking that we were speaking to ourselves, out of our own minds and desires. How do we know when we are talking to ourselves or when the Holy Spirit is directing us? While most of the time the whisperings of the Holy Spirit are subtle, there are times when He is very direct. Let me give you a recent example:
My sister is retired but still drives a school bus on a regular basis to pick up extra cash. Once or twice a year, she and her husband will travel to the coast and spend 2 or 3 nights in a casino, where they both enjoy playing poker with her school bus money. (It's the only money they use for that purpose.) If one or both of them win a poker game or two, they will add that money to the casino fund and save it for the next trip.
On one of the bus trips -- a field trip where the drivers had to wait for the children to return -- another bus driver, a woman also, was telling my sister that one of her checks had bounced at the bank, and now she was faced with not only paying that bill, but also interest and added fees from the bank. She did not know what she was going to do. My sister immediately told the woman to follow her home after they finished their route that day, and she would give her 500 dollars to take to the bank and cover her costs. She took the cash from her casino fund.
The other woman was extremely grateful and promised to repay her 50 dollars every two weeks, with each paycheck. After a couple of payments, however, the woman moved and her bus route was changed, so that the two no longer met on a regular basis. Eventually, my sister began to think to herself, "She's never going to pay me back; I'll never see that money again!" And of course, once we begin to gnaw on a mental bone like that, it continues to haunt us. But then one day, in the midst of her grousing about the money, a strong voice spoke in and to her: "It was never your money to begin with; let it go!" And that voice brought such peace that my sister was able to release all of her negative thoughts and worries about the money. She realized how much of that money she had actually won, as well as earned. She indeed was able to "let it go."
Now how do we know God was speaking in this case? As John McKenzie points out in his book, there is always a sense of the "Other" in these cases. When we are consumed by fear, worry, and anxiety, and there is "voice" that cuts across the direction of our own thoughts, bringing peace and even love, it's a pretty clear indication that we cannot be talking to ourselves. And once we have experienced the Voice of the Holy Spirit speaking to us, we begin to believe and to be a little more sensitive and less doubtful that God does want to be part of our lives.