Related:

• No two identical parts are alike. -- Beach's Law
• No two identical parts are like.
• Software entities are more complex for their size than perhaps any other human construct because no two parts are alike.
  If they are, we make the two similar parts into a subroutine -- open or closed....
• Interchangeable parts aren't. -- Kilpatrick's law
• Interchangeable parts won't. -- The RPCISPE's Eleventh Universal Law
• Identical units tested identically will not behave identically in the field.
  -- The RPCISPE's Eighteenth Universal Law...
• Law of Arbitrary Distinction: Anything may be divided into as many parts as you please.
• Parts that cannot be assembled incorrectly will be. -- The RPCISPE's Tenth Universal Law
• A manuscript for a market in which no textbooks currently exist will be followed two weeks after contracting by an announcement of an identical book by your closest competitor.