Who is Mr. MacPhee from That Hideous Strength and what is their importance?

Mr. MacPhee also lives at the house at St. Anne's, and he is the resident skeptic. He is not a disbeliever, but he holds to objectivity as strongly as possible. He has known Dr. Ransom longer than anyone else in the house, and he is the one who fills Jane in on Ransom's history. However, while recounting this history, with the stories of Mars and Venus, he makes sure to point out that this is all what Ransom said and that it is possible that these were hallucinations. He holds to his objectivity through the end of the novel, but this type of objectivity is open-minded and not markedly proud, so it is not undesirable.