What has happened to Christendom in general according to this teaching?
Christendom in general has been leavened, and Christianity today is leavened. A little false teaching, like yeast in dough, permeates the whole lump, so that all the things Scripture and Christianity once stood against fifty, sixty, or seventy years ago are now part and parcel of everyday experience.
Les explains that the warning in verse 9—'a little leaven, leaveneth the whole lump'—uses yeast as an illustration. Just as yeast in dough does not leaven only a fourth of it but all of it, false teaching works the same way: if a little false teaching is allowed in as leaven, it soon permeates the whole, and one error leads to another. Applying this, Les asks what has happened to Christendom in general and answers that it has been leavened; Christianity today is leavened. The things Scripture and Christianity stood against fifty, sixty, or seventy years ago are now part and parcel of everyday experience. He recalls visiting a church where the world came knocking, and the church said it could accommodate and live with it; then more worldly things came in, and the church again said it could live with that. Now the doors are wide open, and you cannot tell the difference between the church and the world. What happened? A little leaven leavened the whole lump.
A little leaven leaveneth the whole lump.