David Kline, author of Rembrandts in the Attic, has added the following insight from history on the idea that patents are monopolies.
“The condemnation of monopolies ought not to extend to patents, by which the originator of a new process is permitted to enjoy, for a limited period, the exclusive privilege of using his own improvement. This is not making the commodity dearer for his benefit, but merely postponing a part of the increased cheapness (or excellence) which the public owe to the inventor, in order to compensate and reward him for his service.”
John Stuart Mill, “Principles of Political Economy,” 1848
“The dawn of the right of inventors has been actually [contemporaneous] with the destruction of monopolies odious to the common justice of men; and the common sense of mankind has marked a distinction between such monopolies and the exclusive rights conceded to inventors. Their rights, under patents, are called ‘monopolies’ only from the poverty of language, which has failed to express in words a distinction which no less clearly exists.”
Louis Wolowski, Chair of Industrial Economics, Conservatoire des Arts et Métiers, 1864
“How can the exclusive right of an invention be compared with a monopoly in trade? How can the exclusive privilege to sell salt in Elizabeth’s time, which added not one bushel to the production, but which enriched the monopolist and robbed the community, and the exclusive right of Whitney to his cotton gin, which has added hundreds of millions to the products and exports of the country, be both branded, with equal justice, with the odious name of monopoly?”
George H. Knight, 1891
A patent is a property right, it is not a monopoly. For more information see The Myth That Patents are Monopoly.