We’ve got marks on a doorjamb in our house where our kids have measured their height over the years—lines, names, and dates so they can remember how much they’ve grown and so we can reflect on how in the world a boy could grow three jean sizes in six months.

The thing about height is that it can be measured easily—all it takes is a tape measure, a flat edge, and kids who don’t stand on their tiptoes to skew the results.

Sometimes I wish spiritual growth could be measured so easily. I wish I could know that right now I’m 10% further along than I was this time last year, or that facing a particular challenge will advance my spirituality by 8%.

We try to measure it, of course. We track things like church attendance, Bible reading, or prayer frequency. But it doesn’t work well.

Christianity is about growing more and more into the image of Christ, something impossible to quantify. But God does give us a few things that indicate either progress or decline, and we ought to pay attention to those markers. Here’s one of those passages:

About this we have much to say, and it is hard to explain, since you have become dull of hearing. For though by this time you ought to be teachers, you need someone to teach you again the basic principles of the oracles of God. You need milk, not solid food, for everyone who lives on milk is unskilled in the word of righteousness, since he is a child. But solid food is for the mature, for those who have their powers of discernment trained by constant practice to distinguish good from evil (Hebrews 5:11-14).

The writer suggests that one indication of spiritual growth is our willingness to advance beyond the elementary matters of faith. Milk is good, but someone who eats nothing more substantive is either immature or sick. The basics of Christianity are good, but if we’ve been Christians for years and haven’t advanced beyond them, something’s wrong. We should ask: Am I getting deeper into the word than I was a few years ago? Am I more comfortable thinking and talking about serious spiritual matters? Do I enjoy teachers and preachers who challenge me to dive into the meat of the word?

Years ago I took quite a few classes in a field that was different from anything I’d studied before. The professors expected us to read journal articles written by scholars who wrote for their peers, not for uninitiated college students. Quite often I read an entire essay and realized at the end that I understood nothing I’d read.

The interesting thing was—and I guess the professors knew this—as the courses continued, we found ourselves beginning to understand a little of what we read, then a little more, and then finally we could engage in reasonably intelligent conversations about the subject. The essays never became easy, but after a couple of years they made sense. We actually started to enjoy discussing them.

I think something similar happens in matters of faith. Growth comes slowly, and not without struggle. After we’ve stuck with it for a while, we start moving into deeper water. Before too long we’ll look back on where we used to be, and we’ll realize God has led us to higher ground.

It’ll never be measurable, like height or weight, but it’ll make a huge difference in how we approach the stuff in life that really counts. —Chuck