Sat Oct 17 16:40:31 CEST 2009

Informal proofs are difficult

This has bothered me for quite a while.  Formal proofs can be quite
tedious to read, but at least they will not put you in a position
where you're reading a proof and you just can't see why a certain step
is made, because the author assumed it was obvious.

Granted, the ``obvious'' steps usually are obvious, that is from the
perspective of somebody who understands the proof, or has a background
in the matter (i.e. the justification that's left implicit is used a
lot in other proofs).