I cannot think on the one without quickly being encircled by the splendor of the three; nor can I discern the three without being straightway carried back to the one.
Let us not, then, be led to imagine a trinity of persons that keeps our thoughts distracted and does not at once lead them back to that unity. Indeed, the words “Father,” “Son,” and “Spirit” imply a real distinction — let no one think that these titles, whereby God is variously designated from his works, are empty — but a distinction, not a division, The passages that we have already cited [e.g., Zechariah 13:7] show that the Son has a character distinct from the Father, because the Word would not have been with God unless he were another than the Father, nor would he have had his glory with the Father were he not distinct from the Father. . . . “
(Institutes of the Christian Religions, 1:13:17)