The proof builder lets you interactively build proofs using all of the publicly-available theorems and rules of inference. It can make working with proofs easier, apply rules of inference correctly, show what inference rules do and how they work.

**Note** that the proof builder tool needs documentation that does not
yet exist. Today using it is still an adventure. You might like to
start with the version tuned for solving simple math problems
at the Mathtoys website.

Note: *Proof displays and the Proof Builder are supported in recent
versions of Firefox, Chrome, and Microsoft Edge.*