Vatican verifications of healing in people who addressed prayers to a particular holy person is one of the issues that Peter May spoke about. If the claimed miracle meets the criteria of being a miracle – it must be sudden, complete and not relapse – then it can be used as a sign in the canonization of the holy person as a saint. Peter May draws attention to doubtful initial diagnoses of some diseases, and diseases that go into spontaneous remission.
As a practicing Roman Catholic I have heard often of stories of miracles connected both to holy people and holy objects; much of Catholic faith functions in this way. Belief in the communion of saints in this case very literally means that the intercession of saintly people can obtain favours from God. The intercession of saints is asked for after they have died, to obtain things on earth, but also to show proof that the saint now resides in heaven, and didn’t go to the other place.
Peter May was mainly cautioning against naivety in what we believe – belief in something that proves not to be true could actually jeopardize our faith. An over-firm belief in something that later proves to be false, can cause the foundations of faith to crumble. I agree with him – it is wise to weigh things up. It can be better to stand back from a situation and reserve judgment.
But then again should total rationality be allowed to quench the fervour of faith when this faith is legitimate? The blanking out of all things not covered or explained by a general law of nature can become an impoverishment of spirit.