What must be considered in determining priority of invention under 35 U.S.C. § 102(g)?

In determining priority of invention under 35 U.S.C. § 102(g), it is critical to consider both the conception dates and the reasonable diligence of the inventors. This section of the patent law focuses on who first invented the claimed invention, rather than who filed first, which is the underlying principle of the U.S. patent system prior to the switch to a "first to file" system in the AIA.

Conception refers to the complete mental understanding and formation of the invention in the inventor's mind. Reasonable diligence involves the ability of the inventor to proceed with the development and reduction to practice of the invention after conception. This means that even if an inventor conceived an idea first, they must have also demonstrated diligence in bringing the invention into being. If there is a significant gap without development, it may affect their claim to priority.

This balance of conception and diligence is essential because the law recognizes that merely coming up with an idea is not enough; the inventor must actively work toward turning that idea into a functional prototype or a completed invention. Thus, the option that highlights both conception dates and reasonable diligence accurately reflects the legal framework for establishing priority under this section of the U.S. Code.