That’s a great question that was asked of William Ames at the Synod of Dort. I’ve written a book on the Synod of Dort in which I talk about William Ames. He was a great English Puritan who had to flee from England because he wouldn’t conform to the Church of England as a Congregationalist. He found a home in the Netherlands among the welcoming Dutch.
William Ames was the personal secretary to the president of the Synod of Dort in the early seventeenth century, and someone came to him and said, “Is Arminianism a heresy?” This was meant in the old sense of heresy, that is, “Is Arminianism a theological error so serious that it will deprive someone of salvation?” Ames, a staunch Calvinist and staunch Puritan, responded by saying, “No, Arminianism is not a heresy, but it is a serious error tending to heresy.”
In the nine years between the death of Jacob Arminius (the father of Arminianism) in 1609 and the meeting of the Synod of Dort in 1618, Arminianism had radicalized and become more and more Pelagian. So Ames had a sense that Arminianism is an unstable theological position. It may be a position that tries to emphasize grace, but it usually ends up more and more emphasizing free will. Instead of focusing on God it tends to focus on man’s response. The more you focus on man’s response, the greater the danger you are in of moving into a kind of heretical position that religion is about man, not about God.
A number of years ago, J.I. Packer wrote a really helpful and insightful essay called “Arminianisms.” He talks about what he calls “rational Arminianism,” which tends more and more towards Pelagianism and other errors, such as Socinianism, which is a kind of rationalism. Then he contrasts “rational Arminianism” with what he calls “evangelical Arminianism,” particularly related to John Wesley. John Wesley always stressed grace as the priority. He wanted to keep some place for free will, but he wanted to talk about grace and the work of Christ. Packer rightly said that these two Arminianisms are worlds apart.
So you have to ask yourself what kind of Arminianism you are confronting. In its most radical forms it can become a heresy, but in its forms which try to stress grace and responsibility it can be quite evangelical.