Others reduce to practice
Better get it right.
Getting inventorship right on your patent application is more important that you might realize: in litigation, an eagle-eyed attorney could easily break your patent if it can be determined that you knowingly misled the United States Patent and Trademark Office as to who is and is not an inventor on the application.
The United States differs from many other jurisdictions in its focus on inventorship, perhaps because of the perpetuation of the garage-based inventor-tinkerer ideal. In the European Patent Office (EPO) for example, the applicant for the patent doesn’t even have to be the inventor or their agent. There isn’t even a set standard for determining inventorship. Article 60 of the European Patent Convention (EPC) is pretty sparse on the details, and in practice, as per Rule 19 of the EPC "The European Patent Office shall not verify the accuracy of the designation of the inventor." The EPO is much more interested in ownership of the patent.
In contrast to the European laissez-faire attitude, the United States takes inventorship seriously. When filing a patent application, the applicant must also eventually submit an oath asserting that "… he believes himself to be the original and first inventor … " The Federal Circuit has ruled that inventorship, while fact dependant, is ultimately a legal determination.
In practice, an inventor is any individual that has a role in the conception of the invention, as defined by the claims: "The name of the game is the claim." The law allows for a plurality of inventors: "even though (1) they did not physically work together or at the same time, (2) each did not make the same type or amount of contribution, or (3) each did not make a contribution to the subject matter of every claim of the patent" as long as each had a role in the underlying conception of the invention. Conception is another murky legal term which means "the complete performance of the mental part of the inventive act." Note however that the requirement of conception may end up excluding even skilled professionals when they only provide information or suggest ideas or results, but not the means to come to those ideas or results.
However, under the new America Invents Act (AIA), as of September 16, 2012, the USPTO has moved towards greater harmonization with the EPO with regard to the focus on ownership. According to the new rules, the inventor or their agent need not be the party submitting the patent application, now the patent owner (e.g., a corporation, company or other individual) is also granted that right as the applicant and can do so even without the inventor’s oath (holding out as long as right before the patent is to be granted to submit the oath).