Mark Shea has an excellent post on the matter.
Lying is intrinsically sinful.
What does that mean?
It means that no matter what situation you bring up it will never be okay to lie.
What is a lie?
It's knowingly speaking an untruth in order to make them believe it.
What is that intrinsically wrong?
Because our souls are properly ordered towards the Truth.
Now, it is true that the lies mentioned in Mark Shea's blog are not lies that contradict moral, religious or metaphysical truths.
It does not matter.
Everything that exists, all actions, insofar as they are participation in Existence, are Truth. Truth and Existence are different sides of the same coin.
All truths are interrelated, and implicit in one another, this
includes what might be termed worldly truth (like scientific truths), or circumstantial truth (like things I've done, what I wear, what I did, and other ephemeral occurrences.)
We think so long as we strictly adhere to absolute truth, i.e. not lie about our faith or metaphysical truth, then we can lie about ephemeral things in some circumstances.
But no truth is absolutely ephemeral. Because every action, every phenomenon, is performed in time and space, and the fact that it was performed at that time and that space is a permanent truth. For instance, yesterday at about 9:30 am I went to the dry cleaners. That will always be true even though I am no longer at the dry cleaners. And this is true with every other circumstantial truth. They all have a mark of permanence on them.
And insofar as these things are always true, they are Truth. Permanent and absolute.
Now everything a person does should serve the soul's objective which is union with the Ultimate Truth, which is God. Seeking the truth, speaking about it and praising it are not just nice things a soul can do. The soul NEEDS to do these things. And this need is not only on a religious or metaphysical level. The soul craves to know on a worldly and circumstantial truths, which is why it invests so much in science, history and news.
When you understand that the soul needs to operate in truth in order to unite with God, even with respect to relatively ephemeral truths, you understand that it cannot, i.e. should not, lie.Just like you can't make an anus a sexual organ, you can't make a soul a kind of lying organ. The soul was not made for that purpose. And lying is an attempt to make the soul commit an act that is contrary to its own purpose.
And it makes no difference what the circumstances of that lie are. Because no matter what the circumstances are, a lie harms your own soul.
Exterior goals don't change the harm. Intentions don't change the harm. The speakers you're with don't change the harm. Nothing changes the harm of a lie into something good. It can't. The soul was simply not made for that function.
And that is why it is intrinsically wrong.
So please, fellow Catholics: stop the non-sense. There is nothing that justifies lying, not even the pro-life cause. We should put our souls and our spiritual health above everything. Abandoning spiritual truths is what has gotten us into this abortion mess, and abandoning more spiritual truths is not going to get us out of it.