One of the false teachings that St Irenaeus was apparently compelled to refute was a denigration of the material dimension of human existence:
Among the other [truths] proclaimed by the apostle, there is also this one, “That flesh and blood cannot inherit the kingdom of God.” This is [the passage] which is adduced by all the heretics in support of their folly, with an attempt to annoy us, and to point out that the handiwork of God is not saved. They do not take this fact into consideration, that there are three things out of which, as I have shown, the complete man is composed — flesh, soul, and spirit. One of these does indeed preserve and fashion [the man] — this is the spirit; while as to another it is united and formed — that is the flesh; then [comes] that which is between these two — that is the soul, which sometimes indeed, when it follows the spirit, is raised up by it, but sometimes it sympathizes with the flesh, and falls into carnal lusts. Those then, as many as they be, who have not that which saves and forms [us] into life [eternal], shall be, and shall be called, [mere] flesh and blood; for these are they who have not the Spirit of God in themselves. Wherefore men of this stamp are spoken of by the Lord as “dead;” for, says He, “Let the dead bury their dead,” because they have not the Spirit which quickens man. On the other hand, as many as fear God and trust in His Son’s advent, and who through faith do establish the Spirit of God in their hearts, — such men as these shall be properly called both “pure,” and “spiritual,” and “those living to God,” because they possess the Spirit of the Father, who purifies man, and raises him up to the life of God. (AH 5.9.1-2)
Flesh, soul, and spirit—how are we to understand the relationship and distinctions between the three? I imagine this question will arise pretty quickly in our class.
In any case, Irenaeus is most concerned in AH to affirm the goodness and salvation of the material. How is the material saved? By restoring the Spirit to the human being. Without the Spirit the human being is incapable of resisting evil and producing works of holy obedience. Without the Spirit the human being is alienated from the life of God:
The flesh, therefore, when destitute of the Spirit of God, is dead, not having life, and cannot possess the kingdom of God: [it is as] irrational blood, like water poured out upon the ground. And therefore he says, “As is the earthy, such are they that are earthy.” But where the Spirit of the Father is, there is a living man; [there is] the rational blood preserved by God for the avenging [of those that shed it]; [there is] the flesh possessed by the Spirit, forgetful indeed of what belongs to it, and adopting the quality of the Spirit, being made conformable to the Word of God. And on this account he (the apostle) declares, “As we have borne the image of him who is of the earth, we shall also bear the image of Him who is from heaven.” What, therefore, is the earthly? That which was fashioned. And what is the heavenly? The Spirit. As therefore he says, when we were destitute of the celestial Spirit, we walked in former times in the oldness of the flesh, not obeying God; so now let us, receiving the Spirit, walk in newness of life, obeying God. Inasmuch, therefore, as without the Spirit of God we cannot be saved, the apostle exhorts us through faith and chaste conversation to preserve the Spirit of God, lest, having become non-participators of the Divine Spirit, we lose the kingdom of heaven; and he exclaims, that flesh in itself, and blood, cannot possess the kingdom God. (AH 5.9.3)
Whereas his opponents must have preached that freedom is achieved by liberation from the flesh, Irenaeus declares that freedom is achieved by the spiritualizing of the flesh (and soul, I presume) by the Spirit.
How are we to construe spirit and Spirit?