Too many languages

There are thousands of programming languages.

The purpose of a programming language is to express programs. The
purpose of learning programming languages is to build up a toolbox for
reasoning about and synthesizing programs in any one given language.

There are diminishing returns on learning programming languages, and
time is scarce.

Therefore one must select between programming languages to study.

A good selection of languages has both
+ breadth
  + satisfies a number of real world economic needs.
+ focus
  + exploits similarity between languages and incremental learning.
  + some unifying basis

A good member of a particular selection meets a number of the
following criteria:
+ Satisfies one particular school of thought on programming languages.
+ Significant difference from predecessors
+ Significant influence on successors
+ Economically significant
+ Advanced i.e. no direct, established and proven heir.
+ A good language.
  + Easy to express programs with
  + Easy to read programs expressed with
  + Easy to reason about programms expressed with

No one of these criteria are sufficient or even necessary conditions.

A bad member satisfies the opposite criteria.

>>131
The iAPX 432 was designed when anything larger than a 68000 needed multiple chips. With today's technology the whole iAPX 432 takes up less space than the non-cache part of a modern x86 CPU with all its decoder baggage. What are all these transistors being used for? Dynamic translation and out-of-order execution to make an obsolete, hard to decode, inefficient instruction set run fast.