C. S. Lewis had trouble distinguishing between an algebraic variable and a constant

In The Problem of Pain, he wrote:

Suppose that I have a toothache of intensity x: and suppose that you, who are seated beside me, also begin to have a toothache of intensity x. You may, if you choose, say that the total amount of pain in the room is now 2x.

Suppose Lewis has a toothache of intensity quantified as k_1; x is a variable; k_1 is a specific number, a constant.

Now, suppose that you also have a toothache of intensity k_2.

The total amount of pain is k_1 + k_2. If k_1 = k_2 = k, then the total amount of pain is 2k.

We don't have to solve for k; k is a given constant, not a variable.

Lewis continued:

search all time and all space and you will not find that composite pain in anyone's consciousness.

Agreed, but he should have used a symbol like k for a constant and not used x as a variable. Using x could serve his philosophical argument but cause confusion for readers who interpret it mathematically.

You may think that I am being pedantic. I will tell you what actually happened: When I was reading the above, I had trouble understanding what Lewis was trying to say. If x was a variable, it didn't click for me that the x for Lewis and the x for me were identical. I experienced cognitive dissonance, and it took me a couple of minutes to realize that he wasn't talking about a variable but a constant. Then I understood his point.

If you are going to use math terminology, it is better to stick to the technical definition.

See also * Sin, chaos, and entropy