Eiseley speaks in paragraph 15 of “one of those reciprocal matters in which science involves itself.” How is matter reciprocal? What would be “one of those reciprocal matters” today?

the writer needs to avoid using abbreviations and check spelling before sharing.

basic principle: a pronoun usually refers to something earlier in the text (its antecedent) and must agree in number — singular/plural — with the thing to which it refers. the indefinite pronouns anyone, anybody, everyone, everybody, someone, somebody, no one, and nobody are always singular.