Editing Trial and error (section)

===Application===
Traill (2008, ''espec. Table "S" on p.31'') follows [[Niels Kaj Jerne|Jerne]] and [[Karl Popper|Popper]] in seeing this strategy as probably underlying ''all'' knowledge-gathering systems — ''at least in their initial phase''.

Four such systems are identified:
*[[Natural selection]] which "educates" the [[DNA]] of the species,
*The brain of the individual (just discussed);
*The "brain" of society-as-such (including the publicly held body of science); and
*The [[adaptive immune system]].