The core idea is to guess and verify. And since in most cases in New Keynesian Model, we study the linear cases (even if it is not linear, we log linearize), we just need to guess it has a linear form.
The core idea is to guess and verify. And since in most cases in New Keynesian Model, we study the linear cases (even if it is not linear, we log linearize), we just need to guess it has a linear form.