Barclay's personal views, expressed in his own A Spiritual Autobiography (1977) and Clive L. Rawlins' William Barclay: prophet of goodwill: the authorized biography (1998) included:
- scepticism concerning the Trinity: for example "Nowhere does the New Testament identify Jesus with God."
- belief in universal salvation: in his autobiography he wrote, "I am a convinced universalist. I believe that in the end all men will be gathered into the love of God."
- pacifism: "war is mass murder".