How so? For even existence/life is the gift of God, brought about by His power (grace), and thus, even human will is His gift to us, as is our ability to use it. All good and perfect gifts are from above, coming down from the Father of heavenly lights (James 1:17). This includes the gift of freewill, which endows man with the image and likeness of God. To deny this gift of God - the gift of freewill - is to deny the very Love of God which is alone the very motive and source of this gift. This results in a grotesque distortion of the face of God, in the likeness of that distorted face that was presented to our mother, Eve, in the Genesis account. True grace, coming by the Holy Spirit through our faith which brings forth fruits of repentance, illumines our hearts and minds to receive the correct understanding of the Gospel teachings.
As already stated: Grace alone brings us to real knowledge of God. When a person is filled up with enough grace, then there is no need for us not to accept the real meaning of what Paul wrote in his letter to Timothy: that God wills all men to be saved, and to come to knowledge of the Truth (i.e. the knowledge of Him Who says "I am the Truth"), and that it is the misused will of men who prevent this, because God willed this to be allowed. This knowledge is "relational". It proceeds from the experience of personal relationship with the Lord. Many Bible scholars, even those with minds as powerful and brilliant as John Calvin, did not necessarily possess adequate relational knowledge of the saving kind. We will do well to give this possibility great consideration before committing ourselves to their teachings.
Many doctrines of salvation, those produced from the minds of men who were yet, or always too carnal to have the mind of Christ, are false doctrines that distort God's face to those who are taught them. Pride of the intellect, that most difficult if not impossible condition to be overcome and be saved from, is the mother that gives birth to such teachings from men.