PEP 8002: Add a small rationale

pep-8002.rst

@@ -21,6 +21,30 @@ Rather than an individual PEP for each of these community surveys, they will
 all be collected here in this PEP.
 
 
+Rationale
+=========
+
+CPython is not the first open source project to undergo a governance crisis.
+Other projects have experimented various governance options, sometimes several
+times during their existence.  There are useful lessons to take away of their
+experience, which will help inform our own decision.
+
+Project choice
+--------------
+
+There are many open source projects out there, but it will be most fruitful
+to survey those which are similar enough to CPython on a couple key metrics:
+
+1. the number of contributors and their activity (there are scaling issues that
+   don't make the governance models of very small projects very enlightening
+   for our purposes) ;
+2. being mostly or partly community-driven (company-driven projects can afford
+   different governance options, since the company hierarchy has power over
+   the main participants) ;
+3. being faced with important design decisions that require a somewhat formal
+   decision process.
+
+
 Rust
 ====