Most of the first two books of Irenaeus' magnum opus, Against Heresies, are devoted to exposing the heretical teachings of the various sects and their leaders in the late 2nd century that were connected with what we commonly call Gnosticism. Of all the errors of these sects, Irenaeus is most critical of their claims to know more about God than God himself has revealed in Scripture, and their extremely ‘creative’ attempts to prove what they know.
Aware that some Christians might be attracted by the idea of having some secret knowledge about God and the origins of creation revealed to them, Irenaeus issues a warning towards the end of Book II in which he makes clear the dangers of these teachings, both in terms of their content, and the way in which they distort a person's proper relationship to God. He writes,
Preserve therefore the proper order of thy knowledge, and do not, as being ignorant of things really good, seek to rise above God Himself, for He cannot be surpassed; nor do thou seek after any one above the Creator, for thou wilt not discover such. For thy Former cannot be contained within limits; nor, although thou shouldst measure all this universe, and pass through all His creation, and consider it in all its depth, and height, and length, wouldst thou be able to conceive of any other above the Father himself. For thou wilt not be able to think Him fully out, but, indulging in trains of reflection opposed to thy nature, thou wilt prove thyself foolish; and if thou persevere in such a course, thou wilt fall into utter madness, whilst thou deemest thyself loftier and greater than thy Creator, and imaginest that thou canst penetrate beyond His dominions.
It is therefore better and more profitable to belong to the simple and unlettered class, and by means of love to attain to nearness to God, than, by imagining ourselves learned and skilful, to be found among those who are blasphemous against their own God (II.xxv.4, II.xxvi.1).
The problem here, of course, is pride; in claiming to know things that God has chosen not to reveal, the false teachers set themselves over and above God. Their fundamental error, Irenaeus continues, is that 'by the knowledge which he imagines himself to have discovered, he changes God Himself, and exalts his own opinion above the greatness of the Creator' (II.xxvi.3). When you get to this point, Irenaeus suggests it is better to give up all your knowledge, and to simply hold on to one thing:
Nor can there be no greater conceit than this, that any one should imagine he is better and more perfect than He who made and fashioned him, and imparted to him the breath of life, and commanded this very thing into existence. It is therefore better, as I have said, that one should have no knowledge whatever of any one reason why a single thing in creation has been made, but should believe in God, and continue in His love, than that, puffed up through knowledge of this kind, he should fall away from that love which is the life of man; and that he should search after no other knowledge except the knowledge of Jesus Christ the Son of God, who was crucified for us, than that by subtle questions and hair-splitting expressions he should fall into impiety (II.xxvi.1).
As a theologian, Irenaeus would not rule out theological exploration – he lived, of course, in a time when some of most essential doctrines of orthodox Christianity were being formulated. But as a bishop, he also urges us to recognise our limits as creatures, and to be cautious about who we listen to in the pursuit of truth. To that end, Irenaeus offers a simple test to determine whether or not you are on the right track:
A sound mind, and one which does not expose its possessor to danger, and is devoted to piety and the love of truth, will eagerly meditate upon those things which God has placed within the power of mankind (II.xxvii.1).
And that is a word of wisdom the Church today would do well to continue to heed.