Are our thoughts our own? In other words, do we, alone, generate our thoughts in our brain?

If so, can they be influenced and if they can be, who can influence them?

     Where should we start to answer these questions? 

     And does the answer to these questions have anything to do with "free will" and witnessing?

The best place to start is with fallen mankind.  The Bible is clear, to give three of many identical verdicts proclaimed therein, Genesis 6:5 observes, "The Lord saw how great the wickedness of the human race had become on the earth, and that every inclination of the thoughts of the human heart was only evil all the time." Romans 8:7 tells us, "⁷The mind governed by the flesh is hostile to God; it does not submit to God’s law, nor can it do so." and Ephesians 2:1-3a proclaims, "As for you, you were dead in your transgressions and sins, ² in which you used to live when you followed the ways of this world and of the ruler of the kingdom of the air, the spirit who is now at work in those who are disobedient. ³All of us also lived among them at one time, gratifying the cravings of our flesh and following its desires and thoughts." [NIV].

Fallen man's thoughts ARE his own, and even worse, they can be influenced by other fallen men AND the devil and his minions.

Now let's look at saved man.  Jesus teaches his disciples in John 16:13, "But when he, the Spirit of truth, comes, he will guide you into all the 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." and Paul in First Corinthians confirms this in 2:13 when he assures us, "This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, explaining spiritual realities with Spirit-taught words."

Saved man's thoughts are still his own, but now the Holy Spirit is free to influence his thoughts, to the extent that saved man will allow.

In other words, although God certainly CAN influence the thoughts of a fallen man,* He is the Respecter of fallen man's personal desires to be left alone.  He will not influence a man's thoughts until he invites Him to do so.  Man, of his own free will, cannot come to God.

How, then, can fallen man be brought into fellowship with God if of his own free will he chooses to ignore God and even to think and do that which is antithetical to God?  For reasons that only He understands, God has chosen to team up with those people He has saved to create the POSSIBILITY that the unsaved man would consider opening himself up to God.  It is by our spoken and written words and our actions that we can, when working with the circumstances that God orchestrates, set the smallest spark in the fallen man's mind to the possibility that God is real. 

Once that flame of possibility is lit, the fallen man is now open to be influenced by God more and more, so that when he finally does cross over that line that separates non-belief from belief, he can honestly say he had nothing to do with the process: Ephesians 2:8-9, "⁸For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God— ⁹not by works, so that no one can boast."

From the outside, it may appear that he exercised his own free will to make the choice, but in reality, God and his Army of Believers did all the work.

And THAT  is why each of us should take every opportunity we are given to set the smallest spark in the fallen man's mind to the possibility that God is real.   God's Kingdom depends on it.

Thought-93/11/17: My free will aligns with my destiny.

*(For example, see my testimony and the ice skating incident in New Hampshire.)