Every Arminian is a Calvinist at Heart
Have you ever noticed how many prayers attribute God full power of life and salvation, no matter the theological persuasion of the person praying?
Some definitions may be helpful:
Arminian = “Arminianism holds that God’s decision to give salvation to certain persons and not to others is based on his foreknowledge of who will believe. It also includes the idea that genuinely regenerate people can lose their salvation, and that some actually do.” — Millard J. Erickson, The Concise Dictionary of Christian Theology (Wheaton, IL: Crossway Books, 2001), 16.
Calvinism = “The term is applied particularly to the doctrine of predestination, according to which God sovereignly chooses some to salvation not because of any merit or even foreseen faith, but simply by his free will and unmerited grace.” – ibid, 28.

While an Arminian may argue that salvation is the act of God in response to the free will of man in choosing or rejecting God, but have you ever prayed with them? You will find that their prayers are strangely Calvinistic. Even the Arminian will implore God to save the lost, pleading with him to intercede, redeem and regenerate the sinner. Such a request implies that God has sovereign power to move hearts and save individuals.
At the core, before the Creator, every Arminian is a Calvinist at heart.