lization, shift
paradigms or upend cherished beliefs, reorient or revolutionize theoretical
or experimental inquiry, initiate new fields of investigation, conclude
or commence the longest-lived and most emotional squabbles, etc.

<P>In an abstract and generic sense the hardest things are apt to be or
relate to: Demonstrations that a postulated or implied entity or relationship
exists or does not exist, or is possible or impossible; Firm proofs or
disproofs of a proposition or hypothesis; Unifications of an 