to
be imagined; and to imagine a good experiment is as difficult as to
invent a good fable, for we must have distinctly PRESENT--clear mental
vision--the known qualities and relations of all the objects, and must
see what will be the effect of introducing some new qualifying agent.
If any one thinks this is easy, let him try it: the trial will teach
him a lesson respecting the methods of intellectual activity not
without its use. Easy enough, indeed, is the ordinary practice of
experiment, which is either a mere repetition or variation of
experiments already devised (as ordinary story-tellers re-tell the
stories of others), or else a haphazard, blundering way of bringing
phenomena together, to see what will happen. To invent is another
process. The discoverer and the poet are inventors; and they are so
because their mental vision detects the unapparent, unsuspected facts,
almost as vividly as ocular vision rests on the apparent and familiar.

It is the special aim of Philosophy to discover and systematise the
abstract relations of things; and for this purpose it is forced to
allow the things themselves to drop out of sight, fixing attention
solely on the quality immediately investigated, to the neglect of all
other qualities. Thus the philosopher, having to appreciate the mass,
density, refracting power, or chemical constitution of some object,
finds he can best appreciate this by isolating it from every other
detail. He abstracts this one quality from the complex bundle of
qualities which constitute the object, and he makes this one stand for
the whole. This is a necessary simplification. If all the qualities
were equally present to his mind, his vision would be perplexed by
their multiple suggestions. He may follow out the relations of each in
turn, but he cannot follow them out together.

The aim of the poet is very different. He wishes to kindle the emotions
by the suggestion of objects themselves; and for this purpose he must
present images of the objects rather than of any single quality. It is
true that he also must exercise a power of abstraction and selection,
tie cannot without confusion present all the details. And it is here
that the fine selective instinct of the true artist shows itself, in
knowing what details to present and what to omit. Observe this: the
abstraction of the philosopher is meant to keep the object itself, with
its perturbing suggestions, out of sight, allowing only one quality to
fill t