What I'm trying to demonstrate is the concept of comprehensible input, as did second language acquisition scholar Stephen Krashen did in this lecture of his.
We've tried everything else, we've tried grammar teaching, drills and exercises, computers, but the only thing that seems to count is getting messages you understand, comprehensible input.
If comprehensible input is true, what we call the input hypothesis is true. Other things follow from it, and very important, coralary, the input hypothesis is this.
The reason we want to stay in the target language is to get as much comprehensible input as possible – and that is the key, it needs to be comprehensible.