According to recent survey, nearly a third of self-described evangelicals do not believe that Jesus Christ is truly God. Arianism, as it turns out, is a heresy that plagues multiple generations of the Church, not just the one of the fourth century.
Well, over and over the Church has, in various times and ways, ruled that some beliefs are not acceptable alternatives within Christianity. Adherents are, in fact, outsiders to the faith. For example, nearly 100 years ago, in a book entitled Christianity and Liberalism, Presbyterian scholar J. Gresham Machen argued, in an extensive scholarly treatment, that liberal Christianity was not a version of the one, true faith handed down once and for all to the saints. Liberalism was, he argued, a completely different religion from Christianity.