(This is the sixteenth lecture in Stevo Todorcevic’s Forcing class, held in the fall of 2012. You can find the fifteenth lecture here. Quotes by Stevo are in dark blue; some are deep, some are funny, some are paraphrased so use your judgement. As always I appreciate any type of feedback, including reporting typos, in the comments below.)

**Summary**

- This lecture introduces the idea of forcing things that force things to be true.
- Five different types of these theorems are stated.
- We prove one of them. Namely that assuming PFA, after forcing with Sacks, MA is true.