Christian philosophy teaches, in so far as it deals with the relationship between man and these divine forces that are forever building, unbuilding and rebuilding the fabric of life, somewhat as follows: 

The world as we know it, man, life itself as it works through all creation, is the union of matter and spirit; and matter is not spirit, nor spirit matter, nor is one a mode of the other, but they are two different creatures.  Apart from this union of matter and spirit there is no life, in the sense in which we know it, and severance is death.  “The body” says St. Thomas, “is not of the essence of the soul; but the soul, by the nature of its essence, can be united to the body, so that, properly speaking, the soul alone is not the species, but the composite”, and Duns Scotus makes clear the nature and origin of this common “essence” when he says there is “on the one hand God as Infinite Actuality, on the other spiritual and corporeal substances possessing an homogeneous common element.”  That is to say; matter and spirit are both the result of the divine creative act, and though separate, and in a sense opposed, find their point of origin in the Divine Actuality.

The created world is the concrete manifestation of matter, through which, for its transformation and redemption, spirit is active in a constant process of interpenetration whereby matter itself is being eternally redeemed.  What then is matter and what is spirit?  The question is of sufficient magnitude to absorb all the time assigned to these lectures, with the strong possibility that even then we should be scarcely wiser than before.  For my own purposes, however, I am content to accept the definition of matter formulated by Duns Scotus, which takes over the earlier definition of Plotinus, purges it of its elements of pagan error, and redeems it by Christian insight.

“Materia Primo Prima” says the great Franciscan, “is the indeterminate element of contingent things.  This does not exist in Nature, but it has reality in so far as it constitutes the term of God’s creative activity.  By its union with a substantial form it becomes endowed with the attributes of quantity, and becomes Secundo Prima.  Subject to the substantial changes of Nature, it becomes matter as we see it.”

It is this “Materia Primo Prima,” the term of God’s creative activity, that is eternally subjected to the regenerative process of spiritual interpenetration, and the result is organic life.

What is spirit?  The creative power of the Logos, in the sense in which St. John interprets and corrects the early, partial, and therefore erroneous theories of the Stoics and of Philo.  God the Son, the Eternal Word of the Father, “the brightness of His glory and the figure of His Substance.”  “God of God, Light of Light, very God of very God, begotten, not made, being of one substance with the Father:  by Whom all things were made.”  Pure wisdom, pure will, pure energy, unconditioned by matter, but creating life out of the operation of the Holy Spirit on and through matter, and in the fullness of time becoming Incarnate for the purpose of the final redemption of man.