• The Laws of Logic
• Christianity's distinctive, characteristic beliefs

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• The ecumenical councils held the position that only one God exists.
• The positions of the ecumenical councils have stood up to scrutiny for 2,000 years.
• If the positions have stood up to scrutiny for 2,000 years, they are true.
• If the above is true, only one God exists

∴ only one God exists

x only one God exists