I've been reading Francis Schaeffer and the shaping of Evangelical America by Barry Hankins and found the following thought provoking particularly how heresy enters the church..

Commenting on Schaeffers 1972 booklet the new super spirituality and addressing pentecostalism 'that it paralleled liberalism by placing an emphasis on experience over doctrinal content.'....

'Schaeffer tied this to an explanation for how heresy entered the church. He told his readers to imagine that the whole of orthodoxy consisted of 100 points of doctrine. Heresy happens when the church stops teachng, for example, points forty through fifty. Then, someone begins to overemphasize those very points, and because the church has ignored them, people are hungry for them and begin to buy into the overemphasis. The overemphasis is heresy. when another group sees the heretical overemphasis, it starts preaching those points even less than before, even ignoring or attempting to refute them. The proper response, Schaeffer pointed out,is not for the church to ignore points forty through fifty, but to attempt to bring them back into their proper place in the doctrinal system.' (page 152)