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?

I once was lying in bed alone while my mother went to the store,I heard knocking at the door so I thought it was my mother and looked through the peep hole.Then I saw my life flash before my eyes and saw a tall mysterious man who was masked with a weapon I then went to hide as he continued to knock now begging to bang after I hid for 35 minutes my mother cam running inside and gave me a big hug yet she had not known what had happened yet. Was it a trick? I felt very uncomfortable.