In Chapter 7 of The Sovereignty of God, A.W. Pink has the following discussion on the nature of the human will.
What is the Will? We answer, the will is the faculty of choice, the immediate cause of all action. Choice necessarily implies the refusal of one thing and the acceptance of another. The positive and the negative must both be present to the mind before there can be any choice. In every act of the will there is a preference-the desiring one thing rather than another. Where there is no preference, but complete indifference, there is no volition. To will is to choose, and to choose is to decide between two or more alternatives. But there is something which influences the choice; something which determines the decision. Hence the will cannot be Sovereign because it is the servant of that something. The will cannot be both Sovereign and servant. It cannot be both cause and effect. The will is not causative, because, as we have said, something causes it to choose, therefore that something must be the causative agent. Choice itself is affected by certain considerations, is determined by various influences brought to bear upon the individual himself, hence, volition is the effect of these considerations and influences, and if the effect, it must be their servant; and if the will is their servant then it is not Sovereign, and if the will is not Sovereign, we certainly cannot predicate absolute “freedom” of it. Acts of the will cannot come to pass of themselves-to say they can, is to postulate an uncaused effect. Ex nihilo nihil fit-nothing cannot produce something..
He makes an interesting point in this paragraph. He proves that the human will is NOT sovereign. I have struggled with this concept of human free will for a long time. I was always taught that we must choose to accept the gift of salvation when God offers it to us. I also thought that we could choose to reject His offer of salvation. If the will is not sovereign then that calls into question our ability to accept or reject the offer of salvation.
If the will is servant…then servant to what? Pink addresses this a couple paragraphs later. He says
That which determines the will is that which causes it to choose. If the will is determined then there must be a determiner. What is it that determines the will? We reply, The strongest motive power which is brought to bear upon it. What this motive power is varies in different cases. With one it may be the logic of reason, with another the voice of conscience, with another the impulse of the emotions, with another the whisper of the Tempter, with another the power of the Holy Spirit; whichever of these presents the strongest motive power and exerts the greatest influence upon the individual himself is that which impels the will to act. In other words, the action of the will is determined by that condition of mind (which in turn is influenced by the world, the flesh, and the Devil, as well as by God) which has the greatest degree of tendency to excite volition.
So we see here that the will chooses that which has the greatest influence on it. Another way of saying this is that we will choose the thing that we want more and is in agreement with our nature. This is why that an unregenerate person cannot choose God. In their fallen sinful nature the sin has the most influence over their will (For a discussion of how our sinful nature permeates us read this post on Total Depravity). We could actually go a step further and say the the sin nature has control over the will because the will can never choose something against its nature. Pink sums it up this way “if the will is controlled, it is neither sovereign nor free”.
What does all this mean to us? It means that until God chooses to change our nature that we will never be able to choose God. Calvinists call this regeneration. Arminians call it Prevenient Grace. Either way God has to initiate the process of Salvation. We are not free to choose to accept or reject salvation.