John Calvin on the Use of Words to Fight Heresy

"The early Christians, when harassed with the disputes which heresies produced, were forced to declare their sentiments in terms most scrupulously exact in order that no indirect [deception] might remain to ungodly men, to whom [double meaning] of expression was a kind of hiding-place.  Arius confessed that Christ was God, and the Son of God; because the passages of Scripture to this effect were too clear to be resisted, and then, as if he had done well, pretended to concur with others.  But, meanwhile, he ceased not to give out that Christ was created, and had a beginning like other creatures.  To drag this man of wiles out of his lurking-places, the ancient church took a further step, and declared that Christ is the eternal Son of the Father, and consubstantial (of one and the same substance, essence, or nature) with the Father.  The [heresy] was fully disclosed when the Arians began to declare their hatred and utter detestation of the term ὁμοούσιος (homoousios).  Had their first confession, i.e., that Christ was God, been sincere and from the heart, they would not have denied that he was consubstantial with the Father.  Who dare charge those ancient writers as men of strife and contention, for having debated so warmly, and disturbed the quiet of the church for a single word?  That little word distinguished between Christians of pure faith and the blasphemous Arians.  Next Sabellius arose, who counted the names of Father, Son, and Holy Spirit as almost nonentities; maintaining that they were not used to mark out some distinction, but that they were different attributes of God, like many others of a similar kind.  When the matter was debated, he acknowledged his belief that the Father was God, the Son God, the Spirit God; but then he had the evasion ready, that he had said nothing more than if he had called God powerful and just and wise.  Accordingly, he sang another note, i.e., that the Father was the Son, and the Holy Spirit the Father, without order or distinction.  The worthy doctors who then had the interests of piety at heart, in order to defeat this man's dishonesty, proclaimed that three subsistences were to be truly acknowledged in the one God.  That they might protect themselves against tortuous craftiness by the simple open truth, they affirmed that a Trinity of person subsisted in the one God, or (which is the same thing) in the unity of God" (John Calvin, Institutes of the Christian Religion).