What is the warning/point that Aldous Huxley is giving his readers in Brave New World?Please give me some key ideas and examples, including quotes...

In the foreword of Brave New World by
Aldous Huxley states explicitly his theme as the "advancement of science as it affects
human individuals."  Here are some key points of this
theme:

1.  Scientific advances to life are
what change the quality of life.  In Brave New World
there is no longer natural procreation by humans; in fact, the words mother
and father are considered obscene.  In the CENTRAL
LONDON HATCHERY AND CONDITIONING CENTRE, eugenics is used to "predestine and condition"
human beings.  There is a caste system, a system in which people are relatively
content.  This genetic engineering is the truly "revolutionary revolution" that is
acquired in the soul and flesh of the residents of the New World.  For instance, Lenina
tells Henry Foster how repulsive she finds the clothes of the Deltas--"What a hideous
color khaki is"; and, she also finds Epsilons
repellent,

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"I'm glad I'm not an
Epsilon."

"And if you were an Epsilon," said Henry, "your
conditioning would have made you no less thankful that you weren't a Beta or an
Alpha."

In order to make
people love the castes in which they are fashioned, this "deep, personal revolution in
human minds and bodies," sleep conditioning, known as hypnopoedia, is conducted;
children are taught to love their castes, to believe that "everyone belongs to everyone
else," and to believe in consumption and detest nature.  As insurance for this
contentment, soma is distributed so people can go on "holidays"
from reality. When Lenina and Henry go to the Westminster night club, for instance,
soma is served with their coffee. 

2.
Social Stability must be established in order to control
people. In order to deal with dissent and confusion, power must
be centralized and government control increased.  In the New World, there are ten World
Controllers of the totalitarian state, one of whom is Mustapha Mond.  People are
kept "stable in contentment" through their conditioning, and by means of silence about
the truth.  No one reads literature, no one knows any history other than what is
taught.  Time is measured after the year of Our Ford, the year that Henry Ford created
the assembly line method of manufacture. 

Sexual freedom
compensates for diminished economic and social freedom.  Sex is encouraged among people
because it helps people reconcile themselves the "the servitude" which is their fate. 
All individuality has been eliminated as it is dangerous to social
stability.

To make people love their servitude, the
ministries of propaganda control the dissemination of information. One character,
Helmholtz Watson, named by Huxley after the founder of the Behaviorist School of
psychology, John B. Watson, has a distinguished career as an emotional engineer and
writer.  He composes slogans and simplistic rhymes designed to promote the values of
society and pacify people.  And, although he feels that there is more that he could
write, his conditioning prohibits him from appreciating Romeo and
Juliet when John the Savage reads to him in Chapter 12.  He laughs at the
idea of a person loving one person so much.

3.
Despite all the conditioning and stability, man cannot be happy without a
struggle, without suffering.

The character
of John the Savage, born naturally, literate, and human is in total opposition to the
New World.  He alone understands that sorrow must exist if one would be
human,

"All right then...I'm claiming the right to
be unhappy."