Hello. It is not possible to answer your question because you did not provide the excerpt to which this question refers. However, I will try to help you in the best possible way.
Rhetorical strategies are used in a text to influence the reader to agree with the author of a text. In this case, Barry used arguments that convinced the reader about a certain position in relation to scientific research. With that, Barry may have used logical, ethical and / or emotional arguments to get the reader to agree with him.
