only passes by. At the same time, artificial selection also includes,
although it is not limited to, this negative or weeding-out process.
When you select a certain plant for growth in your garden you weed out
the neighbouring plants which encroach upon it, so as to give it a
chance to grow and thrive. By removing its competitors, you let air
and light surround the plant, and it spreads its leaves to the sun.
The healthy growth which results is due to the removal of obstacles
by an external power; and it is in this way--by the removal of
obstacles--that natural selection works.

Intelligent or artificial selection is not restricted to this negative
method of working; and its operation, positive as well as negative,
was certainly well known long before Darwin's day. Starting with the
familiar facts of artificial or purposive selection, Darwin showed how
results similar to those aimed at and reached in this way might be
brought about by the operation of certain natural laws, working
without purpose or design. Purposive selection pursues its ends more
directly and in general attains them far more quickly than does
natural selection. A still more striking characteristic is the fact
that it does not entail the waste and pain which mark the course of
natural selection. Witness the records of natural selection in the
vegetable and animal kingdoms, where thousands are called into
fruitless being that one alone may survive and prosper. Wastefulness
is the most striking feature of its method, and its path is strewn
with wreckage. In all these respects the conflict of ideas belongs
to the level of purposive and not of natural selection. It involves
consciousness of the end, which natural selection never does; it is
comparatively rapid in reaching its goal and comparatively direct in
the route it takes; and the victory of an idea does not take effect
through any general extermination of the individuals who cherish ideas