John 10:30 - Wesley's Explanatory Notes

I and the Father are one — Not by consent of will only, but by unity of power, and consequently of nature. Are — This word confutes Sabellius, proving the plurality of persons: one — This word confutes Arius, proving the unity of nature in God. Never did any prophet before, from the beginning of the world, use any one expression of himself, which could possibly be so interpreted as this and other expressions were, by all that heard our Lord speak. Therefore if he was not God he must have been the vilest of men.