That's an interesting philosophical question and basically depends on whether you consider that God is generally in the business of changing human traits or whether the few hardenings and softenings of heart in the Bible were rare events. Looking at human history in general, I would say that God's interventions - mental or physical - have been extremely sparse. Why didn't he intervene when one lot of Christians were burning another lot of Christians to death? Why didn't he intervene when Christians were persecuting Jews at several stages in history? (It wasn't just Hitler) Jonab responds: as rare as those incidents are it does show that God can influence the heart of man. But for the majority of human history He has chosen not to interfere. Can we conclude that nothing happened without God's acknowledgment(as in the case of Job's suffering)? From the apparent rarity of God's interventions we can probably conclude that most things happen without God's acknowledgement, at least as far as any manifestation on Earth is concerned. Jonab: God may not 'acknowledge' as you say but we can not say that He doesn't know. If He knew Hitler before what Hitler would do and that He could stop Hitler if He chose to then the least we can conclude is God allowed Hitler to do what he did.