C. S. Lewis on the Three Parts of Morality

C. S. Lewis describes two ways in which “the human machine” goes wrong:

One is when human individuals drift apart from one another, or else collide with one another and do one another damage, by cheating or bullying.
The other is when things go wrong inside the individual—when the different parts of him (his different faculties, and desires, and so on) either drift apart or interfere with one another.

He asks us to think of humanity as “a fleet of ships sailing in formation” and what makes it successful:

The voyage will be a success only, in the first place, if the ships do not collide and get in one another’s way; and, secondly, if each ship is seaworthy and has her engines in good order.
As a matter of fact, you cannot have either of these two things without the other.
If the ships keep on having collisions, they will not remain seaworthy very long.
On the other hand, if their steering gears are out of order, they will not be able to avoid collisions.

He then offers an alternative metaphor: “humanity as a band playing a tune.” “To get a good result,” he says, “you need two things”:

Each player’s individual instrument must be in tune and also each must come in at the right moment so as to combine with all the others.

These two elements are fairly obvious, but we often forget to identify the most important piece of information:

We have not asked where the fleet is trying to get to, or what piece of music the band is trying to play.
The instruments might be all in tune and might all come in at the right moment, but even so the performance would not be a success if they had been engaged to provide dance music and actually played nothing but Dead Marches.
And however well the fleet sailed, its voyage would be a failure it it were meant to reach New York and actually arrived at Calcutta.

Applying this to morality, Lewis says that ethics is concerned with three things:

Firstly, with fair play and harmony between individuals.
Secondly, with what might be called tidying up or harmonizing the things inside each individual.
Thirdly, with the general purpose of human life as a whole: what man was made for: what course the whole fleet ought to be on: what tune the conductor of the band wants it to play.

—C.S. Lewis, Mere Christianity, Book 3, Chapter 1 (emphasis added).
Justin Taylor