The Seven Rationales Behind an Obviousness Rejection
Written from MPEP 2143. The MPEP is examination guidance, not law. It binds examiners; it does not bind a court. Current as of 22 August 2026.
MPEP 2143 lists seven rationales an examiner may use to support an obviousness rejection, of which the teaching-suggestion-motivation test that dominated earlier practice is only the seventh.
An obviousness rejection is an argument, and these are the recurring shapes it takes. The section's own title is Examples of Basic Requirements of a Prima Facie Case of Obviousness, so the seven are exemplary rather than exhaustive, more than one can support the same rejection, and naming one is not the rejection. The examiner still has to make the factual findings and connect them to the claim.
Combining known elements to yield predictable results. Simple substitution of one known element for another. Using a known technique to improve similar devices. Applying a known technique to a device ready for improvement. Obvious to try, meaning choosing from a finite number of identified predictable solutions. Adapting known work in one field for use in another. And finally, some teaching, suggestion or motivation in the prior art.
That last one is worth sitting with. It is the test that dominated practice before 2007, the one most people who have read anything about obviousness have heard of, and it now sits at the end of a list of seven. It was not abolished. What the Supreme Court rejected in KSR was treating it as the rigid and exclusive test, not the reasoning itself.
Reading the list as a whole tells you something the individual entries do not: most of these rationales are about combination and adaptation rather than about copying. An examiner does not need a document that shows your invention. They need an argument that the gap between the prior art and your claim was one an ordinarily skilled person would have closed.
The Seven Rationales, A to G
| Rationale | In the manual's words | Turns on predictability |
|---|---|---|
| A | "Combining prior art elements according to known methods to yield predictable results" | Yes |
| B | "Simple substitution of one known element for another to obtain predictable results" | Yes |
| C | "Use of known technique to improve similar devices (methods, or products) in the same way" | No |
| D | "Applying a known technique to a known device (method, or product) ready for improvement to yield predictable results" | Yes |
| E | Obvious to try: "choosing from a finite number of identified, predictable solutions, with a reasonable expectation of" success | Yes |
| F | "Known work in one field of endeavor may prompt variations of it for use in either the same field or a different one based on" design incentives or market forces | No |
| G | "Some teaching, suggestion, or motivation in the prior art that would have led one of ordinary skill to modify the prior art reference" | No |
Four of the seven turn expressly on the result being predictable. That word carries more of the obviousness analysis than any other in this section, and it is the same hinge the KSR combination sentence turns on.
Rationale E is the one aimed at systematic engineering, and all three of its qualifiers are limits: the solutions must be finite in number, identified, and predictable, with a reasonable expectation of success. An unbounded search space, unidentified options, or no reasonable expectation each take a case outside it.
Rationale G's position is the point the list makes concrete. Teaching-suggestion-motivation is not abolished and is not privileged. It is the seventh of seven, so an applicant arguing that nothing in the prior art suggests the combination has answered G and left six standing.
What This Does Not Decide
- It does not say whether any rationale applies to your invention.
- It is not a closed list. Other sections of the manual address further reasoning, and a rationale label alone is not a prima facie case.
- It is not law. The MPEP is guidance for examiners, and a court is not bound by it.
- It does not tell you how to respond to a rejection built on any of these. Describing what a rejection asserts is not the same as answering one.
Educational, not legal advice. Whether any of this reaches a particular invention is a determination for a registered patent practitioner working from the actual prior art.
Sources
- MPEP 2143, Examples of Basic Requirements of a Prima Facie Case of Obviousness
- Back to: is it obvious?