There is an old thought experiment that dates back to the ancient Greeks that surrounds Theseus’ ship. As a youth, I grew up with the stories of Theseus, the six labors, his battle with the minotaur, and the various adventures that surrounded this Greek hero. In his writings, the Historian, Plutarch recorded that Theseus’ ship was left docked in the harbor of Athens as a memorial to the hero, and little by little, as boards began to rot, the Athenians replaced those rotten boards with fresh lumber, preserving the monument.

The thought experiment…the Paradox of Theseus…raises the question, if you are replacing parts of Theseus’ ship, at what point does the ship cease to be Theseus’ ship? Philosophers have debated this for ages and many answers are given to this question. Some argue that when even one board or plank of the ship is replaced, it is no longer Theseus’ ship. Others argue that regardless of how many boards are replaced, it is aways Theseus’ ship. Thomas Hobbes went as far as to raise the question of “what if” when the rotten planks were replaced, someone had taken the old rotten ones, preserved them, and slowly rebuilt Theseus’ ship…then, which one would be the real one?

Aristotle provides us with the main solution to this paradox when he distinguishes between formal causes and material causes. The formal cause — the form that it takes — is not changed even if the actual materials have changed. Thus, in the formal sense, the ship in the harbor is Theseus’ no matter how many boards are changed. One could even replace the wooden boards with plastic ones and the formal cause would remain unchanged even though the material cause was radically different.

From a Christian perspective, while Aristotle is helpful, one might argue that Plato is even more helpful. Plato spoke about forms for things, but argued that the perfect forms exist only in a spiritual realm, or a “World of Forms.” Thus, when we see a circle, what we really see is an imperfect representation of the perfect circle in the world of forms. The same thing can be said about rocks and dogs and even people. There are lots of varieties of each, but each matches a class of entity whose perfect representative exists in the spiritual realm. Thus, Theseus’ ship in the harbor is Theseus’ ship, no matter how many boards are replaced because it is the embodiment of an ideal form. In the case of Hobbes, then, both the ship in the harbor and the preserved rotten ship are Theseus’ ship — both are imperfect physical representations of the original form. Just like there are many dogs, but one “Dog Form,” so too there can be many Ship’s of Theseus.

The Christian philosopher, St. Augustine, fleshed this idea of the Forms out further, locating these forms in the mind of God. God understands the perfect triangle or circle or dog, etc… and the physical world (particularly the fallen physical world) is an imperfect reflection. Thus, while the perfect form of Theseus’ ship exists in the mind of God (remember, all things in this world decay and rot over time), the ship kept in memorial is always Theseus’ ship because it reflects (however imperfectly, whether by decayed wood or replaced timbers) the perfect image in God’s eyes.

Okay, it is an interesting thought experiment, but of what value is it to Christians who no longer really care about Theseus, ancient ships, or Greek Philosophy? On the most basic level, one could argue for the importance of studying reasoning and logic as a part of our growing and maturing as Christians. Indeed, our God is reasonable and is not a God of chaos (1 Corinthians 14:33) and so, the more our lives reflect that the more our lives reflect the character of God. But that would lead us to the more important application of this idea.

We are told in Scripture that humans are made in the image of God (Genesis 1:26-27). This image was not lost in the Fall (Genesis 9:6), but it was clearly distorted, twisted, and bent by sin. In the New Testament we are told that Jesus is the perfect image of the invisible God (Colossians 1:15) and we are being molded and remade into Christ’s image (Romans 8:29). Thus, the life of the Christian is a process by which one is changed from the image of the man of dust into the image of Christ — the man of heaven (1 Corinthians 15:49). We are Theseus’ ship, as it were, constantly having our spiritual planks replaced (sin has rotted them) and being remade and conformed into the image of Christ — a process not complete until we see heaven. Further, while (as Augustine would teach) the perfect circle or the perfect dog exists in the mind of God, the perfect man exists as a person.

Indeed, we are changing. In fact, spiritual stagnation is the worst thing that can happen to the Christian. They become dull, complacent, and no longer engage in the good works for which we were created (Ephesians 2:10). Change into the image of Christ is a mark of the Spirit’s sanctifying work upon our lives. The thing that strikes me is how often (as Christians) we are tempted to want to relive the past — one more shot at the “old man” and not a pursuit of growing as the “new man.” Yet, no matter how much we might wish it otherwise, we can’t go there — we are no longer the person we once were. The planks have been changed. The old ship of Theseus, composed of Hobbes’ rotten boards, won’t float. The new ship in the harbor will, but the new ship is composed of new pieces; if you go back and take out the new pieces and replace them with the old rotten ones, it will sink too. If you want to live…and I mean really live out your identity as an image-bearer of God, then you can only do so with the new boards — the new, sanctified boards. No, I am not the same man I was 27 years ago when I became a believer, but that is a good thing; my life was sinking fast due to the rottenness of sin in my soul; I am grateful for the new boards that God has been constantly replacing in my life. May we all genuinely be grateful for those changes (even the ones that hurt when initially made).