It’s important to get this!:
“Let us take the case of a naturalist who around the year 1700 has set himself the task of describing the pollen grains of the flowers he knows. No doubt he would be able, with the naked eye and the aid of simple magnifying glasses, to find out a good deal by ‘seeing for himself.’ But suppose he is visited by a colleague who has seen such pollen at Delft under one of the first microscopes made by Anton van Leeuwenhoek. Suppose this visitor tells him that the black dust which adheres to one’s hand when one brushes a poppy is in fact a mass of geometric structures of extremely regular shapes which can be clearly differentiated from the pollen granules of all other flowering plants – and so on. Let us assume further that our naturalist has had no opportunity to look through a microscope himself, and has never observed these things which his visitor reports. Granted these assumptions, would not our naturalist be grasping more truth, which means more reality, if he did not insist on regarding as true and real only what he has seen with his own eyes, if on the contrary he could bring himself to ‘believe’ his visitor? In such a situation, what about the rankings of knowledge based upon seeing for oneself and knowledge based upon hearing? Does not hearing and believing take precedence?
Here is the point for us to present in its entirety the sentence of Thomas which we have hitherto abbreviated: ‘Under otherwise similar conditions seeing is surer than hearing; but if the one from whom we learn something by hearing is capable of grasping far more than one could obtain by seeing for oneself, then hearing is surer than seeing.’ Naturally this sentence was originally formulated in regard to belief in the theological sense. But it is equally true of all kinds of belief; belief has the extraordinary property of endowing the believer with knowledge which would not be available to him by the exercise of his own powers.”
– Josef Pieper (13-14)