Why God Can’t Lie (Or Sin)

The idea of an All-Perfect Being lying involves a logical contradiction, just like the idea of a square circle.

Johann Jakob Zeiller, “God the Father” (detail)
Johann Jakob Zeiller, “God the Father” (detail) (photo: Wikimedia Commons)

Scripture repeatedly affirms the truthfulness of God. As early as the book of Numbers, we read:

God is not man, that he should lie, or a son of man, that he should repent. Has he said, and will he not do it? Or has he spoken, and will he not fulfil it? (Num. 23:19).

The same view is expressed in multiple other passages (e.g., 1 Sam. 15:29, 2 Tim. 2:13, Tit. 1:2). Jesus even declares himself to be “the Way, the Truth, and the Life” (John 14:6).

But Hebrews goes a step further, saying not only that God does not lie, but speaking of it being impossible for God to lie:

God, because he wanted to show even more to the heirs of the promise the unchangeableness of his resolve, guaranteed it with an oath, in order that through two unchangeable things, in which it is impossible for God to lie, we who have taken refuge may have powerful encouragement to hold fast to the hope set before us (Heb. 6:17-18, LEB)

How does this square with the fact God is omnipotent—that he can “do anything”?

If he can do anything, wouldn’t that mean he can lie?

No, and here’s why . . .


Talking Nonsense

In my latest book, A Daily Defense, I take up the question of whether God could make up a stone too heavy for him to lift, which poses the same kind of challenge to divine omnipotence that we are considering here.

In response, I point out that theologians do not understand omnipotence to mean that God can do anything you can say.

You can say all sorts of things that amount to gibberish. For example:

God can the helium the the an a five wooden the the the next.

That doesn’t mean anything. It’s just gibberish—nonsense. It doesn’t even obey the laws of English grammar.

And even if something obeys the laws of grammar, that doesn’t mean it makes sense, either.

Linguists have identified sentences like “Colorless green ideas sleep furiously,” which obeys the laws of English grammar but doesn’t mean anything—as long as you give the words their normal meanings.

Taking the terms in their normal senses, this sentence is also jibberish:

God can make colorless green ideas sleep furiously.

But you might not notice that it’s meaningless unless you stopped to carefully parse it. The same is true of sentences like:

God can make four-sided triangles.

God can make square circles.

At first glance, those might sound sensible, but if you think about them, these statements also fall apart.

By definition, a triangle has three sides, not four. And by definition, a circle is not square.

Same thing goes for married bachelors, two-horned unicorns, and colorless green ideas.

None of these things can exist because they all involve logical contradictions. That is, the terms used contradict each other. Philosophers thus classify these entities as logically impossible.

Of course, it is possible to play games with words by taking the terms in non-normal senses, like saying that a four-sided pyramid is a “four-sided triangle” or that a unicorn that later grows a second horn is a “two-horned unicorn,” but that’s not what we’re talking about.

These things are logically impossible if you take the terms in their intended, normal senses.


What Omnipotence Means

This gets us to the issue of omnipotence. It isn’t the ability to do anything you can say—because you can say a lot of things that amount to gibberish—it’s the ability to do anything that is logically possible.

See St. Thomas Aquinas, Summa Theologiae I:25:3-4.

This gives us the answer to whether God can make a stone too heavy for him to lift. The answer is no.

God’s omnipotence gives him unlimited—or infinite—lifting power, and a stone too heavy to be moved with infinite lifting power would have to have more than infinite weight.

And there is no such thing as “more than infinite.”

Even appealing to the different kinds of infinity proposed by mathematicians won’t help, because—as an All-Perfect Being—God’s power comprehends them all, and there is no such thing as a weight that transcends all possible infinities.

A stone too heavy for God to lift thus involves a logical contradiction, meaning it is not logically possible and thus not something an omnipotent Being could create.

But what about lying? Why can’t an omnipotent Being do that? After all, we can!


Why We Can Lie (And God Can’t)

If you think about it a moment, the reason why we can lie becomes clear: It’s because we’re imperfect.

Lying is a sin. Sins are morally imperfect actions. And so a being capable of lying is a morally imperfect being.

That gives us the reason why God can’t sin: He’s All-Perfect, possessing all possible perfections. That means he possesses moral perfection. Moral perfection implies sinlessness. It therefore precludes lying.

To put this in terms of divine omnipotence, the reason God can’t lie—or commit any other sin—is because he’s All-Perfect. If he were able to lie, he would be imperfect, like we are.

The idea of an All-Perfect Being lying thus involves a logical contradiction, just like the idea of a square circle or a married bachelor.

God can’t bring about a situation in which he, an All-Perfect Being, lies any more than he can bring about a situation in which there is a four-sided triangle or a stone too heavy for him to lift.

Such situations are logically impossible because the terms involved contain logical contradictions.

The reason God can’t lie is thus because it’s inconsistent with his nature as an All-Perfect Being.

This idea is reflected in 2 Timothy 2:13, where Paul says that even “if we are faithless, he remains faithful—for he cannot deny himself.”

God’s own nature—his complete holiness—prevents him from sinning.

By the way, if you haven’t already gotten a copy, be sure to check out my book A Daily Defense, where I go into all kinds of interesting things like this!