People also claim that "free will" does not appear in scripture. But "free" and "will" do appear in the same verse, and also "freewill".
So using those verses, we will construct what free will actually is.
1. Free will is a choice, but not an ability.
16 So then it is not of him that WILLETH, nor of him that RUNNETH, but of God that sheweth mercy.
Here, we see a verse making a difference between "willing" something and "running" something.
What Calvinists ignore in this passage is that it doesn't say man doesn't have will (We'll get into compatiblist, that is, limited, free will in a bit, and why that does not exist). It does say man has a will, it just that God trumps whatever the will does.
Point is, people thing that free will means "unlimited ability to execute unlimited choices", when it just means "unlimited choices". Free will is not omnipotence.
So what's the difference? Choosing something does not guarantee you getting what you chose. It depends on your ability to get what you chose, or someone else putting forth their ability.
2. Free will is a desire separate from the action.
17 And the Spirit and the bride say, Come. And let him that heareth say, Come. And let him that is athirst come. And whosoever WILL, let him take the water of life FREELY.
Notice that the will is separate from the action. Willing came before taking.
3. Free will is planning, but not the execution.
13 Go to now, ye that say, To day or to morrow we WILL go into such a city, and continue there a year, and buy and sell, and get gain:
14 Whereas ye know not what shall be on the morrow. For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away.
15 For that ye ought to say, If the Lord WILL, we shall live, and do this, or that.
Planning is free will, the execution and result's are God's. But it cannot be denied that free will came first before God corrects.
4. Free will is of the mouth.
108 Accept, I beseech thee, the FREEWILL offerings of my MOUTH, O Lord, and teach me thy judgments.
10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation.
So what does that mean?
1. When people confuse free will with unlimited ability, and we get things like, "Well, did Lazarus raise himself from the dead? (an ability) So why do you believe you have free will to choose salvation, huehuehuehue? (a choice)".
2. A good rule of thumb based on the prior verses above is, if the mouth (as in voice, not the teeth and all that) can do it, free will can do it. If a mouth can't do it, free will can't do it.
For example, as it states above, by the mouth, confession is made unto salvation. So, a mouth can confess, free will can confess. A mouth can put forth plans. A mouth can make a choice ("Would you like fries with that?", "Yes"). A mouth can put forth desires.
So using the Calvinist strawman above, Lazarus did not raise himself from the dead. He believed in Jesus, a mental act free will can do. Or in salvation, asking Jesus Christ to save you is an act of free will, as, the mouth can do that. Lazarus asking is not the same as raising himself from the dead.
But Calvinists think that someone asking God to save them is equal to someone raising himself from death and taking salvation from force.
3. Now what about compatiblists, ie, man does have free will, but it's limited and can't choose God?
There are no verses that state the will of man is sinful. The heart of man is sinful, the flesh of man is sin is sinful, but nowhere does it state that the will itself is sinful. And nowhere does it state that the will is a slave of heart and flesh. This is just a Calvinist presupposition.
Now, does the heart and flesh have influence on the will? Probably.
But there's more to it than that. The Calvinist assumes that belief in God is an inherently righteous thing, which it is not.
19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
So if belief in God is not inherently righteous, then it is under free will. In fact, God honors belief as righteousness only in specific circumstances afterwards, not before.
6 Even as Abraham believed God, and it was accounted to him for righteousness.
It being counted means it isn't inherently righteous, God had to make it righteous after the act.
Why? Because faith is not works. Righteous acts are works. Faith is not a righteous act until God counts it as such. Which is why the devils' faith does not save them (on top of them not believing Jesus is the Son in the flesh 1 John 4:1-2). if faith is righteous, it makes it a work and thus not anymore grace through faith.
So if free will is simply a choice and not an ability
If faith is neutral, mental act and not a righteous work
Then free will has the power to choose God.