No one Can Believe in Jesus Unless God Grants It
Synergists teach that that we are born as God's children by the will of man but the Bible teaches that we "were born, not of the will of the flesh nor of the will of man, but of God." (John 1:13)
In context verse 13 says,
But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God. John 1:12-13 (King James Version)
The literary structure of these two verses points out that the antecedent efficient cause of "those who received Him" (in faith) is that they were born of God. So, in short, those who receive Christ must, necessarily, be born of God first. Regeneration "unto" faith. verse 13 modifies verse 12.. No one receives him unless God first opens his heart in regeneration. John continues this theme throughout his book in chapter 3 and again in chapter 6. No one can believe in Jesus unless God grants it (John 6:65) and ALL to whom God grants it will believe (John 6:37) The Spirit gives life, the flesh counts for nothing (John 6:63). A syllogism which leaves no room for synergism.
Back to verse 12 & 13: To all who received him... God gave them the power to become sons of God, and they did so not by the will of the flesh or of the will of man but because they were born of God. If you don't read it that way, verse 13 has no meaning. You cannot receive Christ apart from the use of your will and unless the will is renewed, there is no hope of receiving Him.