es, in several ages--though in the
same way--on the surface of our earth.

Summing up--the inventive labor of this period is reduced to creating
increasingly more simple and more rapid methods of _substitution_ in the
commercial mechanism.

The appearance of commerce on a large scale has depended on the state of
agriculture, industry, ways of communication, social and economic
conditions and political extension. It came into being toward the end of
the Roman Republic. After the interruption of the Middle Ages the
activity is taken up again by the Italian cities, the Hanseatic League,
etc.; in the fifteenth century with the great maritime discoveries; in
the sixteenth century by the _Conquistadores_, hungering for adventure
and wealth; later on, by the mixed expeditions, whose expenses are
defrayed by merchants in common, and which are often accompanied by
armed bands that fight for them; lastly comes the incorporation of great
companies that have been wittily dubbed "_Conquistadores_ of the
counting-house."

We now come to the moment when commercial invention attains its complex
form and must move great masses. Taken as a whole, its psychological
mechanism is the same as that of any other creative work. In the first
instance, the idea arises, from inspiration, from reflection, or by
chance. Then comes a period of fermenting during which the inventor
sketches his construction in images, represents to himself the material
to be worked upon, the grouping of stockholders, the making up of a
capital, the mechanism of buying and selling, etc. All this differs from
the genesis of an esthetic or mechanical work only in the end, or in the
nature of the images. In the second phase it is necessary to proceed to
execution--a castle in the air must be made a solid structure. Then
appear a thousand obstructions in the details that must be overcome. As
everywhere else, minor inventions become grafted on the principal
invention; the author lets us see the poverty or richness in resource of
his mind. Finally, the work is triumphant, fails, or is only
half-successful.

Did it keep only to these general traits, commercial imagination would
be merely the reiteration, with slight changes, of forms already
studied; but it has characteristics all its own that must be
distinguished.

(1) It is a combining or tactical imagination. Heretofore, we have met
nothing like it. This special mark is derived from the very nature of
its determinis