ith old
ones. Is such criticism or thought easy? Far from it. It has difficulties
of its own. These are of two varieties: the difficulty of showing people
who are content with their present stock of old ideas that the new ones
are interesting or important; and the great difficulty of making _new_
ideas clear and intelligible, for the art of being clear and perfectly
intelligible is very, very hard to acquire and to practise. The third kind
of criticism--the third kind of thought--the kind that is at once both
destructive and constructive--has a double aim--that of destroying old ideas
that are false and that of replacing them with new ideas that are true;
and so the third kind of criticism or thought is the most difficult of
all, for it has to overcome both the difficulty of destructive criticism
and that of constructive thought.

The reader, therefore, if he will be good enough to reflect a little upon
the matter, can not fail to appreciate the tremendous difficulties which
beset the writing of this little book, for he must perceive, not only that
the work belongs to the third kind of critical thought, but--what is much
more--the errors it aims to destroy are fundamental, world-wide and old,
while the true ideas it seeks to substitute for them are fundamental and
new. This great difficulty, felt at _every_ stage of this writing, is, for
a reason to be presently explained, greatly enhanced and felt with
especial keenness in the present chapter. I therefore beg the reader to
give me here very special cooperation--the cooperation of open-mindedness,
candor and critical attention. It is essential to keep in mind the nature
of our enterprise as a whole, which is that of pointing the way to the
science and art of Human Engineering and laying the foundations thereof;
we have seen Human Engineering, when developed, is to be the science and
art of so directing human energies and capacities as to make them
contribute most effectively to the advancement of human welfare; we have
seen that this science and art must have its basis in a true conception of
human nature--a just conception of what Man really is and of his natural
place in the complex of the world; we have seen that the ages-old and
still current conceptions of man--zoological and mythological conceptions,
according to which human beings are either animals or else hybrids of
animals and gods--are mainly responsible for the dismal things in human
history; we have seen tha