John Calvin, Sermons on the Deity of Christ, Sermon 1
[Speaking of those who found support for the doctrine of the Trinity in the writings of pagan philosophers]
Now those who are so curious as to wish thus to make the Philosophers agree with Holy Scripture think they do great service to the Christian Church when they can say that the Gospel-writers have not been the only ones who have spoken thus and that even the pagans have well known such things. It is very apropos! As though one put a veil before clear vision. Behold God Who makes Himself clear to us by the doctrine of His Gospel, and we are going to put a veil before it by saying, “Look at this! Your clearness will be still more clear.”
It is very certain that God willed that these same things might be known by pagan Philosophers to render them so much more inexcusable before His Majesty. But that is not to say that His doctrine ought to be confirmed by what they have said. For the fact is that, although the more they thought they were approaching God, the further away they were straying. So is fulfilled this sentence which Saint Paul pronounces against all mankind. All those who wished to be too clever, who did not seek God in such reverence and humility as they ought, have fallen into the depth of error. And it is a just punishment from God if we come thus to pollute His doctrine, classing it among the foolish inventions of men.