In the Third Test, this premise has been underlined by the three confident lbw appeals Sachin Tendulkar survived against Dominic Cork. The first came on Thursday when he had made five and the other two on the second morning when he was well past a hundred.
On all three occasions, the Sri Lankan umpire, Kandiah Francis, gave the decision. He will have had his reasons for giving the batsman the benefit of the doubt. As long as he is consistent, no one can complain.
In contemporary Test cricket, every decision is replayed ad infinitum on television and analysed to death. If the pundits decide that the ball was going down the leg side or doing too much or bouncing too high, or that it hit the pad fractionally outside the line of the off-stump, the umpire is pilloried for giving the batsman out.
Small wonder that he wants to be absolutely sure that he has not made a mistake before he raises his finger. Francis is a conscientious umpire who will have weighed up the pros and cons in his mind and, feeling that on each occasion there was an element of doubt, gave it unerringly to the batsman.
It is worth pointing out, too, that while those of us whose job it is to pontificate on these things have the chance to see endless slow-motion replays, the umpire has only one chance to see what happened, and at full speed. It is not surprising that the umpires tend more and more to err on the side of caution.
Then there is the Bird factor. Over his career no umpire has been more respected than Bird and in the trade he has been very definitely known as a "not-outer". Aspiring umpires will have seen where this approach has taken him and will not have been slow to follow suit. Umpires who are forever raising their fingers are seldom given high marks over a long period.