In T 1799/08 the board stated that it is not the function of the boards of appeal to carry out a general review of decisions at first instance, regardless of whether such a review has been sought by the parties. In view of the character of the inter partes appeal proceedings, it could not be expected that the board, independently of its preliminary opinion on some of the critical issues for deciding on a ground not properly substantiated by the opponent which had initially raised it, would fully investigate that ground, in breach of the principle of equal treatment of the parties, and provide its own reasoning, substituting itself for an opponent which remained passive. The board thus accepted, in the absence of any evidence to the contrary, the patent proprietors' arguments.