This is the post #21 of the Calvin's Institutes summary series.
Human beings are deprived of free will because we are all sinners. Sin is our nature. Even though we have some power left in us to investigate and understand earthly things, we are stripped of any power to understand and pursue heavenly things. We still choose freely, in that we can will without compulsion, yet, we only choose sinfully, and so our will does not deserve to be called "free." Even for regenerated Christians, we are constantly in need of the Holy Spirit's power for us to will what is spiritually good.
(This was another long and difficult chapter. My summary is awfully inadequate here. However, one thing is clear from this chapter: every good thing comes from God and we, human beings, owe Him everything.)