Mere Christianity | Study Guide

C.S. Lewis

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Mere Christianity | Book 4, Chapter 4 : Beyond Personality: Or First Steps in the Doctrine of the Trinity (Good Infection) | Summary



Lewis addresses temporal cause and effect as it relates to the three-person nature of God. God the Father begets Christ the Son, but this does not mean God's existence predates Christ's. Lewis explains the relationship between Christ and the Father by comparing it to the act of imagining a mental image. The act causes the image, but both act and image happen at the same moment in time. God has been imagining Christ always, since the beginning of time. One is no less eternal than the other. Christ "is the self-expression of the Father—what the Father has to say."

But both are Persons, which is why the Bible refers to the Father and the Son. This language communicates the "relation of love" between God and Christ. Lewis turns to the maxim "God is love," critiquing it for its implications that love implies a subject and an object whereas God is undifferentiated. He says the real Christian meaning is "Love is God," as love is an eternal, creative attribute of God.

Lewis says the Christian God is different from gods in other religions because it is neither a person nor is it static. The Christian God is more like a "dance" or "drama." The interplay between Father and Son gives rise to the third person of the "three-personal" God, the Holy Spirit or Holy Ghost.

From a human perspective, it is helpful to think of the Holy Ghost as the part of God that is within us. The Father, meanwhile, stands "in front" and the Son stands next to us, "trying to turn [us] into another son." We achieve the happiness that is our birthright by allowing the three-person drama of God to play itself out within us. We enter this dance by sharing in the life of Christ, whose purpose is to spread the "good infection" of the spiritual life (Zoe) among humankind. When we have Christ in us, we assume Christ's relation to God the Father, and as a result, the Holy Spirit manifests within us.


Lewis opens the chapter by invoking the idea of simultaneous causation to explain the paradox of Christ as the begotten son who is also as eternal as the one who begot him. Simultaneous causation functions both as a metaphysical and physical, or scientific, hypothesis about the nature of cause and effect and therefore about the structure of the universe. As such it is a topic among theologians, philosophers, and scientists alike.

The nature of cause and effect, when considered superficially in terms of ordinary life experience, might seem so obvious as to be a nonissue. A slightly deeper consideration of the issue reveals its incredible complexity. For example, do cause and effect necessarily have a temporal, or time-based, relationship, and if so, in what sense?

Philosophers struggle with the idea that the universe has a cause, because if there was no time before the universe began there were also no causes. Cosmologists (scientists who work on understanding how the universe began and developed) sometimes consider the idea of the Big Bang in terms of simultaneous causation. The cause of the universe and the universe itself could come into being at the same moment. This theory is commonly described by the scientific notation t=0, meaning time equals zero. Physicists like Stephen Hawking see simultaneous causation as a way to explain the creation of the universe without having to invoke God, a supernatural force, to bridge the gaps in the theory. The reader may find it interesting that Lewis uses simultaneous causation to explain his theistic cosmology (theory about the universe's origin and development) while simultaneous causation allows Hawking to advance a plausible atheistic cosmological theory.

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