Theologian R. B. Kuiper believed that John Calvin would’ve completely supported the 5-points of Calvinism (see Charles Partee, “The Theology of John Calvin,” 128. footnote 13); Kuiper said in light of his view on Calvin:

Calvinism is the most nearly perfect interpretation of Christianity. In the final analysis, Calvinism and Christianity are practically synonymous. It follows that he who departs from Calvinism is taking a step away from Christianity. For in the last instance the fundamentals of Calvinism are also the fundamentals of the Christian religion. (R. B. Kuiper, As To Being Reformed, cited by Charles Partee, The Theology of John Calvin, 128.fn.13)

Come on, admit it, this describes you; you think Calvinism is the Gospel “TULIP” style. All those outside this pale, just might be outside the orthodox; indeed, may not be a Christian at all, right? 😉