Intro.:  The basic purpose of the Establishment Clause is, in the
words of Thomas Jefferson, to erect “a wall of separation between the
church and state.”  However, this famous quote is terribly helpful.
Some examples of blatant violations, discussed in Everson:
1.    Neither a state nor the feds may set up an official church.
2.    Government may not “force [or] influence a person to go to or
to remain away from church against his will or force him to profess a
belief or disbelief in any religion.”
3.    No one may be “punished for entertaining or professing
religious beliefs or disbeliefs, for church attendance or
non-attendance.”
4.    Government may not prefer one religion over another.  Also,
government may not prefer religion to non-religion.
5.    Government may not participate in the affairs of religious
organizations, and such orgs may not participate in the affairs of
government.