A patent is property carried to the highest degree of abstraction—a right in rem to exclude, without a physical object or content.

I have been so constantly under the necessity of watching the movements of the most unprincipled set of pirates I have ever known, that all my time has been occupied in defense, in putting evidence into something like legal shape that I am the inventor of the Electro-Magnetic Telegraph.
From a letter to his brother describing the challenge of defending his patents (19 Apr 1848).

In the world's history certain inventions and discoveries occurred of peculiar value, on account of their great efficiency in facilitating all other inventions and discoveris. Of these were the art of writing and of printing, the discovery of America, and the introduction of patent laws. The date of the first ... is unknown; but it certainly was as much as fifteen hundred years before the Christian era; the second—printing—came in 1436, or nearly three thousand years after the first. The others followed more rapidly—the discovery of America in 1492, and the first patent laws in 1624.

Next came the patent laws. These began in England in 1624, and in this country with the adoption of our Constitution. Before then any man [might] instantly use what another man had invented, so that the inventor had no special advantage from his own invention. The patent system changed this, secured to the inventor for a limited time exclusive use of his inventions, and thereby added the fuel of interest to the fire of genius in the discovery and production of new and useful things.

That reminds me to remark, in passing, that the very first official thing I did, in my administration—and it was on the first day of it, too—was to start a patent office; for I knew that a country without a patent office and good patent laws was just a crab, and couldn't travel any way but sideways or backways.

The cigar-box which the European calls a 'lift' needs but to be compared with our elevators to be appreciated. The lift stops to reflect between floors. That is all right in a hearse, but not in elevators. The American elevator acts like a man's patent purge—it works.

The Congress shall have power to ... promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.
Founding U.S. Patents.

The Constitution never sanctioned the patenting of gadgets. Patents serve a higher end—the advance of science.

The Patent Office is the mother-in-law of invention.

The patent system was established, I believe, to protect the lone inventor. In this it has not succeeded. … The patent system protects the institutions which favor invention

Well, the people, I would say. There is no patent. Could you patent the sun?" [On being asked who owned the patent on his polio vaccine by journalist, Edward R. Murrow in 1954.]

[No one will be able to] deter the scientific mind from probing into the unknown any more than Canute could command the tides.
Comment upon the U.S. Supreme Court's 1980 decision permitting the patenting of life forms.