Heidegger (the other one) on the use of reason in theology

"Illumined reason is of no contemptible use to theology. And its chief use consists in that it brings forth from its own treasury arguments on behalf of faith. This happens in four ways. Firstly, reason urged and directed by the Spirit of God through sure and undoubted criteria and signs of divinity discovers that he who reveals the way of salvation, God, is not an imposter, demon or man suspected of falsehood. Secondly, illumined reason puts forth arguments for the principles of the Christian faith by which it shows to the unbelieving of those who embrace it its worthiness of credit, which is not a thing impossible, irrational or contrary to man's uncorrupted nature; and it dissolves subtleties adduced to the contrary by a perverse reason. Thirdly, reason occasionally proceeds in accordance with its own principles by collecting suitable arguments on behalf of faith., in those matters which are known both by faith and by reason; or arguments at least known by faith, which stimulates reason in many, are confirmed by reason. Fourthly, in a word reason, accompanying the use of words and of the things signified by these words, whether natural ideas and reasons which we have of and for the things and which revelation presupposes, has power of judgment on equal terms, ie, those considered apart from construction of conjunction. Use is the judge in familiar words which are not proper and peculiar to revelation. Faith alone judges upon the supernatural construction and conjunction of simple words or terms which belong to revelation alone. The Holy Spirit alone secures our right use of reason and the propriety of our faith."

Johannes Heidegger, Corpus Theologicae