Last week, in Arendi S.A.R.L. v. Apple, the Federal Circuit reversed a Patent Trial and Appeal Board (PTAB) finding of invalidity in an inter partes review that relied on “common sense” to supply a claim limitation that was not disclosed by the prior art. When used to support a finding of obviousness, common sense is typically applied to provide a motivation to combine references, rather than to provide a limitation that is missing from the prior art. The court’s decision in this case is worth noting because it signals the Federal Circuit’s growing concern about conclusory PTAB findings of obviousness that are not supported by the record.