Men must always have distinguished (e. g. in judicial matters) between hearsay and seeing with one's own eyes and have preferred what one has seen to what he has merely heard from others. But the use of this distinction was originally limited to particular or subordinate matters. As regards the most weighty matters the first things and the right way the only source of knowledge was hearsay.
Alexander Fleming
In my first publication I might have claimed that I had come to the conclusion, as a result of serious study of the literature and deep thought, that valuable antibacterial substances were made by moulds and that I set out to investigate the problem. That would have been untrue and I preferred to tell the truth that penicillin started as a chance observation. My only merit is that I did not neglect the observation and that I pursued the subject as a bacteriologist. My publication in 1929 was the starting-point of the work of others who developed penicillin especially in the chemical field.
