What are patents for?

I've seen many answers to this question on various discussion forums. Generally it is answered by asserting that patents are supposed to promote innovation, protect inventors and/or their companies or "promote the Progress of Science and useful Arts." as per Section 8 of the US Constitution.

I would argue that all those answers are correct but that the underlying reason that explains why they're all correct is often missed.

Although not stated explicitly in the legislation, the core concept behind any patent system is a bargain between the inventor and the State. This can be paraphrased as 'you agree to tell the public all about your invention and in return we give you a temporary monopoly on that invention within our borders'. In practice, the requirement to tell the public all about the invention is met by publishing the patent application describing the invention and ensuring that a patent application must disclose enough information that the skilled person can recreate the invention.

This bargain has a number of knock-on effects. By offering an incentive to disclose the details of an invention, patents help to disseminate the knowledge underlying that invention and so 'promote the progress of Science and useful Arts.' Allowing a temporary monopoly on an idea encourages other inventors to 'invent around' the monopoly in the happy knowledge that if they can do so, they too will obtain a monopoly on their new way of doing the same thing. This encourages innovation. Finally, the establishment of a temporary monopoly is of course a powerful aid for the inventor seeking to capitalise on his invention, whether by starting his own company or selling his invention to another company. In that sense, patents can protect the small inventor or company.

On the whole, patent legislation says a great deal about what can and can't be patented, who can apply for them and how one sets about making an application. However, they don't say very much at all about why the legislation has been enacted in the first place, or what it is intended to achieve. For example, the preamble to the UK Patents Act merely states that what you are about to read is intended to establish a new law of patents. Similarly, the preamble to the European Patent Convention simply refers to a desire to "strengthen co-operation between the States of Europe in respect of the protection of inventions", without saying anything about why this protection is necessary.

This is probably because current patent systems have evolved from earlier legislation, so that the rationale behind the system no longer needs to be spelt out. Wikipedia has an interesting article on the history of patent law (http://en.wikipedia.org/wiki/Patent) and provides a good place for the interested reader to start.

- Richard