That must be deployed?

that must be deployed? that must be deployed by whom?

Context:

I did not gain the impression that the theologians who mounted
this evasive defence were being wilfully dishonest. I think they were
sincere. Nevertheless, I was irresistibly reminded of Peter
Medawar's comment on Father Teilhard de Chardin's The
Phenomenon of Man, in the course of what is possibly the greatest
negative book review of all time: 'its author can be excused of dis-
honesty only on the grounds that before deceiving others he has
taken great pains to deceive himself'. The theologians of my
Cambridge encounter were defining themselves into an
epistemological Safe Zone where rational argument could not reach
them because they had declared by fiat that it could not. Who was
I to say that rational argument was the only admissible kind of
argument? There are other ways of knowing besides the scientific,
and it is one of these other ways of knowing that must be deployed
to know God.