In T 493/88 (OJ 1991, 380) the board held that a decision of an opposition division rejecting an opposition had not been correctly reasoned within the meaning of R. 68(2), first sentence, EPC 1973 if, after giving the reasons why the opposition division, unlike the opponent, considered the subject-matter of the patent to be new, it failed to state the reasons why it considered that the subject-matter also involved an inventive step.
Where there was no explanation of how the examining division had arrived at its conclusion that the claimed process was an obvious juxtaposition of certain documents, this was held insufficient T 292/90).
In T 153/89 the examining division had given no reasons for finding in its decision that the subject-matter of the dependent claims was not inventive. The board of appeal took the view that the perfunctory statement in the contested decision did not permit the board to judge whether this issue had been sufficiently investigated, or investigated at all. The examining division's decision on such grounds did not amount to a reasoned decision.
In T 698/94 neither the minutes of the oral proceedings before the opposition division nor the appealed decision itself contained the slightest hint at the arguments brought forward by the parties. It was impossible for the parties to the proceedings to see how the opposition division had arrived at its conclusion of lack of novelty. The losing party was deprived of its legitimate right to challenge the reasoning on which the decision was based, which was the very purpose of proceedings before the boards of appeal (see G 9/91, OJ 1993, 408).
In T 1747/06 the board distinguished the situation before it from that in T 856/91, where the board had held that an incomplete decision did not constitute a breach of R. 68(2) EPC 1973 since it was sufficient for a decision to be reasoned in some way, even if the reasoning was incomplete and deficient. According to the board in T 1747/06, T 856/91 dealt with the specific question of whether or not references in the reasoning of the decision to the knowledge of recognized experts and to a statement of a recognized expert in the context of what a person skilled in the art could derive from a specifically cited prior art document, without it being clear who these experts were or what exactly the statement was, resulted in the decision being not reasoned. The board concluded that the decision was reasoned even if the reasoning was incomplete and deficient. In the case at issue in T 1747/06, however, no reasoning was given at all (see also point 4.2.2 a) above).