Elements of the philosophy of the human mind. By Dugald Stewart. Rev. and abridged, with critical and explanatory notes, for the use of colleges and schools. By Francis Bowen ...

182 INVENTION.
proceed, it may be proper to take notice of the distinction between invention and discovery. The object of the former, as
has been frequently remarked, is to produce something which
had no existence before; that of the latter, to bring to light
something which did exist, but which was concealed from common observation. Thus we say, Otto Guerricke invented the
air-pump; Sanctorius invented the thermometer; Newton and
Gregory invented the reflecting telescope; Galileo discovered
the solar spots; and Harvey discovered the circulation of the
blood. It appears, therefore, that improvements in the arts are
properly called inventions, and that facts brought to light by
means of observation are properly called discoveries.
Agreeable to this analogy is the use which we make of these
words, when we apply them to subjects purely intellectual. As
truth is eternal and immutable, and has no dependence on our
belief or disbelief of it, a person who brings to light a truth
formerly unknown is said to make a discovery. A person, on
the other hand, who contrives a new method of discovering
truth, is called an inventor. Pythagoras, we say, discovered
the forty-seventh proposition of Euclid's first book; Newton
discovered the binomial theorem; but he invented the method
of prime and ultimate ratios, and he invented the method of
fluxions.
In general, every advancement in knowledge is considered as a
discovery; every contrivance by which wue produce an effect, or
accomplish an end, is considered as an invention. Discoveries
in science, therefore, unless they are made by accident, imply
the exercise of invention; and accordingly, the word invention is
commonly used to express originality of genius in the sciences
as well as in the arts. It is in this general sense that I employ
it in the following observations.
fHow inventions are made. - It was before remarked, that, in
every instance of invention, there is some new idea, or some new
combination of ideas, which is brought to light by the inventor;
and that, although this may sometimes happen in a way which
he is unable to explain, yet when a man possesses an habitual
fertility of invention in any particular art or science, and can